Đốt cháy hoàn toàn m gam este đơn chức X cần vừa đủ 20,16 lít O₂, sản phẩm thu được gồm 17,92 lít CO₂ và 7,2 gam H₂O (các thể tích khí đo ở điều kiện tiêu chuẩn). Mặt khác, khi thuỷ phân X trong môi trường kiềm thì thu được 2 muối. Có bao nhiêu công thức cấu tạo thoả mãn tính chất của X là

A. 3.

B. 1.

C. 4.

D. 5.

Khi lai giữa hai cá thể động vật (P) đều có kiểu hình mắt đỏ, chân cao, F₁ thu được tỉ lệ 1 mắt đỏ, chân thấp : 2 mắt đỏ, chân cao : 1 mắt trắng, chân cao. Biết rằng mỗi tính trạng do một gen quy định, quá trình giảm phân bình thường, không xảy ra đột biến gen và đột biến NST, sự biểu hiện của tính trạng không phụ thuộc vào môi trường. Khẳng định nào sau đây là đúng về sự di truyền của các tính trạng?

A. Các gen quy định các tính trạng nằm trên các NST khác nhau.

B. Các gen quy định các tính trạng cùng nằm trên một NST, có ít nhất một cá thể của P không xảy ra hoán vị gen.

C. Các gen quy định các tính trạng cùng nằm trên một NST, cả hai cá thể của P đều không xảy ra hoán vị gen.

D. Các gen quy định các tính trạng nằm trên cùng một NST, hoán vị gen xảy ra với tần số 50%.

Có 5 ống nghiệm được đánh số theo thứ tự (1), (2), (3), (4), (5). Mỗi ống nghiệm chứa một trong các dung dịch AgNO₃, ZnCl₂, HI, Na₂CO₃, NH₃. Biết rằng:

- Dung dịch trong ống nghiệm (2) và (3) tác dụng với nhau sinh ra chất khí.

- Dung dịch trong ống nghiệm (2) và (4) không tác dụng được với nhau.

- Dung dịch trong ống nghiệm (5) tác dụng với 1 hoặc 4 đều có hiện tượng kết tủa rồi tan.

Các chất có trong các ống nghiệm (1), (2), (3), (4), (5) lần lượt là

A. ZnCl₂, HI, Na₂CO₃, AgNO₃, NH₃.

B. AgNO₃, Na₂CO₃, HI, NH₃, ZnCl₂.

C. AgNO₃, HI, Na₂CO₃, ZnCl₂, NH₃.

D. AgNO₃, HI, ZnCl₂ ,Na₂CO₃

Giải phương trình: |-5x| - 16 = 3x

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.

Animals have an intuitive awareness of quantities. They know without analysis the difference between a number of objects and a smaller number. In his book “The Natural History of Selboure” (1786), the naturalist Gilbert White tells how he surreptitiously removed one egg a day from a plover’s nest, and how the mother laid another egg each day to make up for the missing one. He noted that other species of birds ignore the absence of a single egg but abandon their nests if more than one egg has been removed. It has also been noted by naturalists that a certain type of wasp always provides five - never four, never six -caterpillars for each of their eggs so that their young have something to eat when the eggs hatch. Research has also shown that both mice and pigeons can be taught to distinguish between odd and even numbers of food pieces.

These and similar accounts have led some people to infer that creatures other than humans can actually count. They also point to dogs that have been taught to respond to numerical questions with the correct number of barks, or to horses that seem to solve arithmetic problems by stomping their hooves the proper number of times.

Animals respond to quantities only when they are connected to survival as a species - as in the case of the eggs - or survival as individuals - as in the case of food. There is no transfer to other situations or from concrete reality to the abstract notion of numbers. Animals can “count” only when the objects are present and only when the numbers involved are small - not more than seven or eight. In lab experiments, animals trained to “count” one kind of object were unable to count any other type. The objects, not the numbers, are what interest them. Animals’ admittedly remarkable achievements simply do not amount to evidence of counting, nor do they reveal more than innate instincts, refined by the genes of successive generations, or the results of clever, careful conditioning by trainers.

What is the main idea of this passage?

A. Of all animals, dogs and horses can count best

B. Careful training is required to teach animals to perform tricks involving numbers

C. Although animals may be aware of quantities, they cannot actually count

D. Animals cannot “count” more than one kind of object

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 35 to 42.

TEACHING IN INDIA

by Elise Cooper

  ‘Elise in India’. That was the name of my blog last year when I took a year out between school and university. I was lucky enough to get a teaching job abroad through an international organization. I was going to work in a school attached to a children’s home in north-west India. There were eight of us on the week-long introduction course in the capital, Delhi. As well as advice and ideas for teaching we were given information about health and local customs, and learned a few essential phrases in the local language.

  Another course member, Lucy, was coming to the same school as me and we were both nervous when we set off on the 15-hour bus ride to the children’s home. I had worked as a classroom assistant before, but here I wouldn’t be much older than some of my pupils. How would I manage? My worries disappeared once we reached the home. Our rooms were on the top floor above the girls’ bedrooms and from the window we looked out across flat fields full of fruit trees and could just see the snow-covered mountain tops in the distance.

  There were 90 children in the home, aged between five and 20. In addition there were a small number of pupils who came in each day from the area around. Although they were a little shy to start with, they were so keen to ask us questions that we quickly became friends.

  Lucy and I taught four lessons a day, mainly spelling, reading and general knowledge. We had a textbook but since it wasn’t very exciting, we tried to make the lessons more interesting with activities and games. This wasn’t always easy: there was a mixture of ages in each class because pupils had begun their education at different times. Like schoolchildren everywhere, they didn’t always behave perfectly in class. However, they used to send us notes apologizing afterwards, or thanking us for an interesting lesson, so we didn’t really mind.

  The best fun came after school, though. We spent many happy hours playing games or football or just chatting with the children. On Friday afternoons, Lucy and I were in charge of sport, which had just been introduced at the school. Trying to organize fifty children into cricket teams is something I’ll never forget. Another of my memories is playing in goal for a boys’ football game. Even though Lucy and a group of little girls joined in as extra goalkeepers, we still managed to let the other side score!

  I was terribly sad to leave. I felt I had learned as much as - if not more than - my pupils from the experience.

Which of the following words would the author most probably use to describe her experience in India?

A. useful

B. problematic

C. informative

D. nonsense