Phép nhân các số tự nhiên, phân số, số thập phân có chung các tính chất nào dưới đây?

A. Tính chất giao hoán

B. Tính chất kết hợp

C. Tính chất nhân một số với một tổng

D. Cả ba tính chất trên

Trong các khẳng định sau khẳng định đúng là:

A. Nếu a.b > 0 thì a và b là hai số nguyên dương

B. Nếu a.b > 0 thì a và b là hai số nguyên âm

C. Nếu a.b = 0 thì a = 0 và b = 0

D. Nếu a.b < 0 thì a và b là hai số nguyên khác dấu

Read passage and mark the letter A, B, C, or D to indicate the correct word or phrase that best fits each of the numbered blanks from 29 to 33.

We can (29) _______ other people in many different ways. We can talk and write, and we can send messages with our hands and faces. There is also the phone (including the mobile!), the fax, and e-mail. Television, film, painting, and photography can also communicate ideas.

Animals have ways of exchanging information, too. Bees dance and tell other bees where (30) _______ food. Elephants make sounds that humans can’t hear. Whales sing songs. Monkeys use their faces to show anger and love. But this is nothing (31) _______ to what people can do. We have language - about 6,000 languages, in fact. We can write poetry, tell jokes, make promises, explain, persuade, tell the truth, or tell lies. And we have a sense of past and future, not just present.

Radio, film, and television (32) _______ a huge influence on society in the last hundred years. And now we have the Internet, which is infinite. But what is this doing to this? We can give and get a lot of information very quickly. But there is (33) _______ information that it is difficult to know what is important and what isn’t. Modem media is changing our world every minute of every day.

Điền ô số 30

A. finding

B. found

C. to find

D. they find

Trung Quốc có những điều kiện thuận lợi nào để phát triển các ngành công nghiệp khai thác, luyện kim và sản xuất hàng tiêu dùng?

Tiến hành các thí nghiệm sau:

          - Thí nghiệm 1: Cho a gam bột nhôm vào dung dịch H₂SO₄ (loãng, dư), thu được V₁ lít khí không màu.

          - Thí nghiệm 2: Cho a gam bột nhôm vào dung dịch KOH (dư), thu được V₂ lít khí không màu.

          - Thí nghiệm 3: Cho a gam bột nhôm vào dung dịch HNO₃ (loãng, dư), thu được V₃ lít khí không màu (hóa nâu trong không khí, sản phẩm khử duy nhất của N⁺⁵).

Biết các phản ứng xảy ra hoàn toàn, thể tích các khí đo ở cùng đktc. So sánh nào sau đây đúng? 

A. V₁ = V₂ = V₃.    

B. V₁ > V₂ > V₃. 

C. V₃ < V₁ < V₂

D. V₁ = V₂ > V₃.

Nêu một số nhân tố bên trong ảnh hưởng đến sinh trưởng và phát triển của động vật.

Cho các chất sau đây

(1) H₂N-CH₂-COOH.

(2) HOOC-CH₂-CH(NH₂)-COOH.

(3) H₂N-CH₂-CH(NH₂)-COOH.                  

(4) ClH₃N-CH₂-COOH.

(5) HOOC-CH₂-CH(NH₂)-CH₂-COONa.    

(6) NaOOC-CH₂-CH(NH₂)-COONa

Những chất lưỡng tính là

A. (2),(4) và(3).

B. (1),(2),(3), (6).

C. (1), (2),(3),(4) và (5).

D. (1), (2),(3) và (5).

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 question.

        Most people start smoking when they are in their teens and are addicted by the time they reach adulthood. Some have tried to quit but have returned to cigarettes because smoking is such a strong addiction. It is a habit that is very difficult to break. There are many different reasons why people smoke.

        Three of the main reasons that young people smoke are to look mature, to be like their friends, and to experiment. Since teens see older people all around them smoking, especially their parents and relatives, they smoke to act older. If their friends or peers smoke, they may feel pressured into doing the same to be accepted. The last reason is the excitement of experimenting with something that is forbidden. In Massachusetts it is against the law for anyone under 18 years old to smoke. Usually parents do not allow their under age teens to smoke. Therefore, smoking becomes very attractive. It is exciting to get cigarettes and sneak away to smoke without being caught.

         Adults smoke for other reasons. They may have a lot of stress and pressures because of economic and personal problems. They may be unemployed or working but not making enough money to take care of themselves and their families. They may be homeless, or they may be dealing with alcohol or cocaine/heroin addictions. Some may be in bad marriages or relationships in which there is physical and/or verbal abuse. All these people may smoke to feel relaxed or to give them energy while going through a hard time.

        Whether young or old, some people smoke to control their weight. Smokers, on the average, weigh seven pounds less than non-smokers. Smoking reduces a person's appetite. It lessens his/her sense of taste and smell. This could be why ex-smokers gain weight after quitting cigarettes. Food tastes and smells so much better.

        Finally, there are people who say they love to smoke. Smoking gives them pleasure. It just makes them feel good.

The word “peers” in paragraph 2 means

A. members of the aristocracy

B. mentors

C. peeping Toms

D. persons of a similar age