Để nhận biết Gly-Ala và Gly-Gly-Gly-Ala trong hai lọ riêng biệt, thuốc thử cần dùng là:

A. Cu(OH)₂

B. NaOH

C. HCl

D. NaCl

Hai chất nào sau đây đều tác dụng được với dung dịch NaOH loãng ?

A. ClH_­3NCH_­2­COOC_­2­H_­5­ và H_­2­NCH_­2­COOC_­2­H_­5­

B. CH_­3­NH_­2­ và H_­2­NCH_­2­COOH

C. CH_­3­NH_­3­Cl và CH_­3­NH_­2­

D. CH_­3­NH_­3­Cl và H_­2­NCH_­2­COONa

thèn này ko làm mà lôi BTVN ra hỏi lmj z ?

Một chiếc thuyền đi trong nước yên lặng với vận tốc có độ lớn v 1 , vận tốc dòng chảy của nước so với bờ sông có độ lớn . Nếu   v 2 người lái thuyền hướng mũi thuyền dọc theo dòng nước từ hạ nguồn lên thượng nguồn của con sông thì một người đứng trên bờ sẽ thấy

A. thuyền trôi về phía thượng nguồn nếu  v 1 > v 2

B. thuyền trôi về phía hạ lưu nếu  v 1 > v 2

C. thuyền đứng yên nếu  v 1 < v 2

D. truyền trôi về phía hạ lưu nếu  v 1 = v 2

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 43 to 50.

The need for a surgical operation, especially an emergency operation, almost always comes as a severe shock to the patient and his family. Despite modern advances, most people still have an irrational fear of hospitals and anaesthetics. Patients do riot often believe they really need surgery- cutting into a part of the body as opposed to treatment with drugs.

          In the early year of the 20^th century, there was little specialization in surgery. A good surgeon was capable of performing almost every operation that had been advised up to that time. Today the situation is different. Operations are now being carried out that were not even dreamed of fifty years ago. The heart can be safely opened and its valves repaired. Cloyed blood vessels can be clean out, and broken ones mended and replaced. A lung, the whole stomach, or even part of the brain can be removed and still permit the patient to live a comfortable and satisfactory life. However, not every surgeon wants to, or is qualified to carry out every type of modern operation. 

          The scope of surgery has increase remarkable in the past decades. Its safety has increased, too. Deaths from most operations are about 20% of what they were in 1910 and surgery has been extended in many directions, for example, to certain types of birth defects in new born babies, and at the other end of the scale, to life-saving operation for the octogenarian .The hospital stay after surgery has been shortened to as little as a week for most major operations. Most patients are out of bed on the day after an operation and may be back at work in two or three weeks.

          One of the most revolutionary areas of modern surgery is that of organ transplants. Until a few decades ago, no person, except an identical twins, was able to accept into his body the tissues of another person without reacting against them and eventually killing them. Recently, however, it has been discovered that with the use of X-rays and special drugs, it is possible to graft tissues from one person to another which will survive for periods of a year or more. Kidneys have been successfully transplanted between non-identical twins. Heart and lung transplants have also been reasonably successful.

          “Spare parts” surgery, the simple routine replacement of all worn-out organs by new ones, is still a dream of the future but surgery is ready for such miracles. In the meantime, you can be happy if the doctors say to you: “Yes, l think it is possible to operate on you for this condition”.

Surgeons in the early 20^th century compared with modern ones ______.

A. had less to learn about surgery.

B. needed more knowledge.

C. were more trusted by their patients.

D. could perform every operation known today.

Read the following andmark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

Harvard University, today recognized as part of the top echelon of the world's universities, came from very inauspicious and humble beginning.

This oldest of American universities was founded in 1636, just sixteen years after the Pilgrims landed at Plymouth. Included in the Puritan emigrants to the Massachusetts colony during this period were more than 100 graduates of England's prestigious Oxford and Cambridge universities, and these universities graduates in the New Word were determined that their sons would have the same educational opportunities that they themselves had had. Because of this support in the colony for an institution of higher learning, the General Court of Massachusetts appropriated 400 pounds for a college in October of 1636 and early the following year decided on a parcel of land for the school; this land was in an area called Newetowne, which was later renamed Cambridge after its English cousin and is the site of the present-day university.

When a young minister named John Harvard, who came from the neighboring town of Charlestowne, died from tuberculosis in 1638, he willed half of his estate of 1,700 pounds to the fledgling college. In spite of the fact that only half of the bequest was actually paid, the General Court named the college after the minister in appreciation for what he had done. The amount of the bequest may not have been large, particularly by today's standard, but it was more than the General Court had found it necessary to appropriate in order to open the college.

Henry Dunster was appointed the first president of Harvard in 1640, and it should be noted that in addition to serving as president, he was also the entire faculty, with an entering freshmen class of four students. Although the staff did expand somewhat, for the first century of its existence the entire teaching staff consisted of the president and three

The main idea of this passage is that ______________.

A. Harvard University developed under the auspices of the General Court of Massachusetts

B. What is today a great university started out small

C. John Harvard was key to the development of a great university

D. Harvard is one of the world's most prestigious universities

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions below.

Because writing has become so important in our culture, we sometimes think of it as more real than speech. A little thought, however, will show why speech is primary and writing secondary to language. Human beings have been writing (as far as we can tell from surviving evidence) for at least 5000 years; but they have been talking for much longer, doubtless ever since there have been human beings.

When writing did develop, it was derived from and represented speech, although imperfectly. Even today there are spoken languages that have no written form. Furthermore, we all learn to talk well before we learn to write; any human child who is not severely handicapped physically or mentally will learn to talk. a normal human being cannot be prevented from doing so. On the other hand, it takes a special effort to learn to write. In the past many intelligent and useful members of society did not acquire the skill, and even today many who speak languages with writing systems never learn to read or write, while some who learn the rudiments of those skills do so only imperfectly.

To affirm the primacy of speech over writing is not, however, to disparage the latter. One advantage writing has over speech is that it is more permanent and makes possible the records that any civilization must have. Thus, if speaking makes us human, writing makes us civilized.

In the author’s judgment, ______.

A. writing has more advantages than speech

B. writing is more real than speech

C. speech conveys ideas less accurately than writing does

D. speech is essential but writing has important benefits

Hòa tan hết 25,76 gam hỗn hợp Fe, FeO, Fe₂O₃ và Fe₃O₄ vào 1,24 lít dung dịch HNO₃ 1,0 M thu được V lít NO (đkc) và dung dịch X. Dung dịch X hòa tan tối đa 12,88 gam Fe. Biết NO là sản phẩm khử duy nhất của N⁺⁵. Giá trị của V là:

A. 0,896

B. 1,12

C. 1,344

D. 2,24