Giải bất phương trình: x - 2 < 4

Điều nào sau đây là chưa chính xác ?

A. Công thức tổng quát của một anđehit no, mạch hở bất kỳ là C_nH_2n+2–2kO_k (k: số nhóm –CHO).

B. Một anđehit đơn chức mạch hở bất kỳ, cháy cho số mol H₂O nhỏ hơn số mol CO₂ phải là một anđehit chưa no.

C. Bất cứ một anđehit đơn chức nào khi tác dụng với lượng dư dung dịch AgNO₃/NH₃ cũng tạo ra số mol Ag gấp đôi số mol anđehit đã dùng.

D. Một ankanal bất kỳ cháy cho số mol H₂O luôn bằng số mol CO₂.

* 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.

  Most volcanoes are found along an imaginary belt, called the Ring of Fire, that encircles the Pacific Ocean. However, volcanic activity takes place in many far-flung regions of the world such as Hawaii, Iceland, Europe, and even the floor of the earth’s oceans. The leading theory as to why volcanic activity, as well as earthquakes, takes place when and where it does is called the theory of “plate tectonics”. The theory holds that the outer shell of the earth is divided into many different rigid sections of rock, called plates. These plates are not static, they are in continuous motion over a layer of partly melted rock. While their movement may appear insignificant, at only several inches per year, it is not. Indeed, the collisions between plates caused by this almost imperceptible movement can have catastrophic consequences. Volcanic activity and earthquakes are concentrated near the boundaries of these giant, moving plates.

  The majority of volcanoes are formed at te point where two plates collide. One of the plates is forced underneath the other. As the plate sinks, the earth’s heat and the friction of the movement cause a portion of the sinking plate to melt. This melted portion of plate is called magma, and when it reaches the earth’s surface it becomes a volcano. Volcanoes can also be created when two plates begin to diverge. Then, magma from below the earth’s crust moves up to fill the void between the two plates. Large quantities of lava spill out from the void. Volcanoes of this type usually are found not on land, but on the ocean floor. In extreme instances this can lead to the formation of gigantic, sunken mountain ranges like Mid-Atlantic Ridge that spans nearly the entire length of the Atlantic Ocean. The theory of plate tectonics also explains why some volcanic activity takes place so far from any known plate boundaries. Basically, these volcanoes are the result of huge column of magma, or plumes, that rise up and break through the surface of the earth.

It can be inferred from the passage that____________.

A. Plates are very unlikely to move a kilometer in a year 

B. Most earthquakes may be prevented 

C. The Mid- Atlantic Ridge is visible from land 

D. The plates will eventually stop moving

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions.

The only members of the cat family that can roar are lions, leopards, tigers, and jaguars but lions are by far the loudest.

A. Like leopards, tigers, and jaguars, lions are among the members of the cat family that can roar.

B Since lions come from the same cat family as leopards, tigers and jaguars do, they can roar as loud as the others.

C. Lions, leopards, tigers, and jaguars are the only four cats that can roar; however, the others can’t roar as loudly as lions do.

D. The roar of a lion is loud enough to make other animals, such as leopards or tigers, feel frightened.

Read the following passage and mark the letter A, B, C or D on the answer sheet to indicate

the correct answer to each of the following questions:

   University Entrance Examination is very important in Vietnamese students. High school graduates have to take it and get high results to be admitted to universities. The pressure on the candidates remains very high despite the measures that have been taken to reduce the heat around these exams, since securing a place in a state university is considered a major step towards a successful career for young people, especially those from rural areas or disadvantaged families. In the year 2004, it was estimated that nearly 1 million Vietnamese students took the University Entrance Examination, but on average only 1 out of 5 candidates succeeded. Normally, candidates take 3 exam subjects, and each lasts; 180 minutes for the fixed group of subjects they choose. There are 4 fixed groups of subjects: Group A: Mathematics, Physics, and Chemistry; Group B: Mathematics, Biology, and Chemistry; Group C: Literature, History, and Geography; Group D: Literature, Foreign Language, and Mathematics.

   In addition to universities, there are community colleges, art and technology institutes; professional secondary schools, and vocational schools which offer degrees or certificates from a-few-month to 2-year courses.

   According to Vietnam's Ministry of Education and Training, there are currently 23 non-public universities, accounting for 11% of the total number of universities. These non-public universities are currently training 119,464 students, or 11.7% of the total number of students. The government is planning to increase the number of non-public universities to 30% by 2007.

Which sentence refers to the University Entrance Examination in Vietnam?

A. Students find it easy to get success in the University Entrance Examination.

B. Math is compulsory in the University Entrance Examination.

C. Students are not allowed to choose their exam subjects.

D. There are four fixed groups of exam subjects for students to choose.

Polime được tổng hợp bằng phản ứng trùng ngưng là 

A. poli(vinyl clorua) 

B. poli(etylen-terephtalat) 

C. poliacrilonitrin

D. polietilen