Khi nói về chuỗi và lưới thức ăn, phát biểu nào sau đây là đúng?

A. Tất cả các chuỗi thức ăn đều được bắt đầu bằng sinh vật sản xuất.

B. Một loài có thể tham gia nhiều chuỗi thức ăn khác nhau trong quần xã.

C. Thực vật không thể tham gia vào các sinh vật tiêu thụ.

D. Trong một quần xã, mỗi loài sinh vật chỉ tham gia vào một chuỗi thức ăn.

Tơ nilon-6,6 là sản phẩm trùng ngưng của

A. axit ađipic và glixerol

B. axit ađipic và hexametylenđiamin

C. etylen glicol và hexametylenđiamin

D. axit ađipic và etylen glicol

Cho sơ đồ phản ứng :

(a) X + H₂O → xúc   tác  Y

(b) Y + AgNO₃ + NH₃ + H₂O ® amoni gluconat + Ag + NH₄NO₃

(c) Y → xúc   tác E + Z

(d) Z + H₂O → chất   diệp   lục ánh   sáng X + G

X, Y, Z lần lượt là :

A. Tinh bột, glucozơ, cacbon đioxit

B. Tinh bột, glucozơ, etanol

C. Xenlulozơ, saccarozơ, cacbon đioxit

D. Xenlulozơ, fructozơ, cacbon đioxit

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.

Househusbands

Dear Editor,

I read with interest the article on American families. In general I agree with it, but there are some important things it left out. It didn't tell the reader much about the life of a househusband. It's not an easy life. I know, because I'm now a househusband myself. A househusband has to change many of his ideas and his ways.

First of all, he has to change the way he thinks about time. Before I was a househusband, I worked full-time for the New York Times. I was a reporter, and time was always important. We had to finish our article quickly and give them to the editor. Everyone was always in a hurry. This is the way, many other men work, too. Businessmen, lawyers, bankers, and doctors all have to work quickly.

At home it's different. The househusband cannot be in a hurry all the time. If you rush around, you will make everyone unhappy! The children will be unhappy because they don't understand. For them, time is not important. Your wife will be unhappy because the children are unhappy. You will be unhappy, too, because they are all unhappy. So you have to learn to slow down. That is the first and most important rule for a househusband.

There is something else the househusband must learn. You must learn to show how you feel about things. At work, men usually do not talk about feelings. If they do, people think they are strange. So, many men are not used to telling anyone about their feelings. They do not know how to talk about their anger, worries, or love. But children need to know how you feel. They need to know how much you love them. If you are angry, they need to know why. Your wife also needs to know about your feelings. If you do not say anything, your family may get the wrong idea. Then there may be serious problems.

People talk a lot about househusbands these days. Usually they talk about men doing the housework, the cooking, cleaning, and shopping. But in my opinion, these are the easiest things to learn. It was much harder for me to change the way I think and the way I act with my family. I think, other men will also find this harder, but, like me, will find it necessary if they want to have a happy family!

Ted Diamond

The word "rush" in paragraph 3 is closest in meaning to ______ .

A. spend time idly.

B. move about very slowly. 

C. shout loudly and angrily.

D. move about hurriedly.

X là este mạch hở được tạo bởi từ một axit cacboxylic đa chức và một ancol đơn chức, trong X chỉ chứa một loại nhóm chức. Hiđro hóa hoàn toàn X bằng lượng H₂ vừa đủ (xúc tác Ni, t⁰), thu được este Y có công thức phân tử là C₆H₁₀O₄. Số đồng phân có thể có của X thỏa mãn các điều kiện trên là 

A. 3

B. 2

C. 1. 

D. 4

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

Many scientists _____ all their lives to working out answers to problems.

A. send

B. promote

C. spend

D. devote

Hệ cân bằng sau xảy ra trong một bình kín:

CaCO3 (r) → CaO(r) + CO2 (k), ΔH > 0

Điều gì xảy ra nếu thực hiện một trong những biến đổi sau?

a) Tăng dung dịch của bình phản ứng.

b) Thêm CaCO3 vào bình phản ứng.

c) Lấy bớt CaO khỏi bình phản ứng.

d) Thêm ít giọt NaOH vào bình phản ứng.

e) Tăng nhiệt độ.

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

Four West Indian geckos, with human assistance, have recently entered the United States. The yellowheaded gecko, the ashy gecko, the reef gecko, and the ocellated gecko are presently inhabiting the tropical areas of the Keys and the tip of southern Florida. The Mediterranean gecko also arrived along the Gulf coast some time ago, via the West Indies. The only other geckos in the United States live in the Southwest. In extreme southern California, the leaf-gingered gecko lives in dry, rocky country and scampers over boulders at night, hiding by day in crevices. It has a slender, tapered tail and stalks insects by raising itself high on its legs, cocking its head, and twitching its tail nervously before leaping on its prey. In courtship, the tail is also waved by the male as he approaches the female.

Although most lizards are excellent climbers, the geckos are able to walk on smooth surfaces with the help of unique clinging devices under the toes. Also, the undersides of most geckos have pads of large scales, each of which bear microscopic hairs with hundreds of branches having minute, blunt ends that press against the surface that the gecko is on, enabling the gecko to cling to almost any surface. Like other lizards, geckos have the ability to shed their tails if attacked by an enemy. They stump heels and a new tail is grown in approximately the same shape as the original. Unlike most lizards, most geckos have no moveable eyelids. The nocturnal geckos have vertical pupils, which contract in bright light. All geckos, except several New Zealand species, lay eggs. The eggs have a tough, white shell and are laid under stones, behind window shutters or under bark.

What is the most likely subject of the paragraph following this passage?

A. Information on how baby geckos hatch and develop

B. The story of the journeys of West Indian geckos

C. A description of geckos native to North America

D. A history of the southern California desert

Nhà nước Văn Lang ra đời để giải quyết những yêu cầu gì của xã hội