Một giống lúa có alen A gây bệnh vàng lùn, để tạo thể đột biến mang kiểu gen aa có khả năng kháng bệnh này người ta tiến hành các bước sau:

(1) Chọn lọc các cây có khả năng kháng bệnh.

(2) Xử lí hạt giống bằng tia phóng xạ để gây đột biến, gieo hạt mọc thành cây.

(3) Cho các cây con nhiễm tác nhân gây bệnh.

(4) Cho các cây kháng bệnh lai với nhau hoặc tự thụ phấn tạo dòng thuần.

Thứ tự đúng là:

A. (1) → (2) → (3) → (4)

B. (2) → (3) → (4) → (1)

C. (2) → (3) → (1) → (4)

D. (1) → (3) → (2) → (4)

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.

What Do You Think?

We have all had bad experiences with restaurants, stores, or hotels. Maybe you have gone to a restaurant that served terrible food. Perhaps you have gone to a store that had high prices or bad service. Or maybe you have booked a hotel and found out later that the room was nothing like the advertisement.

These days, we have a better chance of preventing these unpleasant surprises. We can do this by using apps. “App” is short for “application”. An app is a computer programme on a smartphone. You can use apps to do almost anything. Apps can help you play games, get directions, talk to friends, and so on.

If f you want to find information about a store or a hotel, you can use a review app. Review apps help us evaluate services and products before we hand over our money. The idea is very simple. After you go to a restaurant or stay in a hotel, you can post a review with one of your apps. You can say anything you want. If you like a hotel you stayed in, you can tell people that it was wonderful. If you think that the food in a certain restaurant was bad, then you tell people not to eat there. Other people can use their apps to read your reviews.

Plenty of people prefer not to use these review apps. Many of these people prefer to go out and decide for themselves whether or not a service is good. However, review apps are getting more and more popular every day. Some apps are for specific services. For example, Tripadvisor focuses on travel, and Goodreads focuses on books. There are also other, larger apps that provide information for just about every service that you can think of.

The phrase “is short for” in paragraph 2 can best be replaced by ________.

A. stands for

B. supports

C. takes after

D. offers

Chất Y có công thức cấu tạo CH₃COOCH=CH₂. Tên gọi của Y là 

A. metyl acrylat

B. propyl fomat

C. metyl axetat

D. vinyl axetat

Công thức phân tử của metyl metacrylat là 

A. C₅H₁₀O₂

B. C₄H₈O₂. 

C. C₅H₈O₂

D. C₄H₆O₂

Hợp chất X có công thức cấu tạo là HCOOCH=CH₂ . Tên gọi của X là: 

A. vinyl fomat

B. etyl axetat

C. vinyl axetat

D. metyl fomat

Một vật thực hiện dao động điều hòa theo phương trình: x = 8cos(20πt + π/2) cm; thời gian đo bằng giây. Chu kỳ, tần số dao động của vật là:

A. T = 20 s; f = 10 Hz

B. T = 0,1 s; f = 10 Hz

C. T = 0,2 s; f = 20 Hz

D. T = 0,05 s; f = 20 Hz