Cho các phát biểu sau:

(1) Anđehit vừa có tính oxi hóa vừa có tính khử.

(2) Phenol tham gia phản ứng thế brom khó hơn benzen.

(3) Anđehit tác dụng với H₂ (dư) có xúc tác Ni đun nóng, thu được ancol bậc một.

(4) Dung dịch axit axetic tác dụng được với Cu(OH)₂.

(5) Dung dịch phenol trong nước làm quỳ tím hóa đỏ.

(6) Phương pháp hiện đại để sản xuất CH₃CHO là oxi hóa không hoàn toàn etilen.

Số phát biểu đúng là

A. 4.                     

B. 2.                     

C. 5.                     

D. 3.

Nông nghiệp Bắc Mĩ phát triển mạnh mẽ, đạt đến trình độ cao nhờ điều kiện tự nhiên thuận lợi và kĩ thuật tiên tiến. Đặc biệt, Hoa Kì và Ca-na-đa có tỉ lệ lao động trong nông nghiệp rất thấp nhưng sản xuất ra khối lượng nông sản rất lớn.

Hoa Kì và Ca-na-đa có diện tích đất nông nghiệp lớn và trình độ khoa học kĩ thuật tiên tiến, nhờ đó đã phát triển được nền nông nghiệp hàng hoá với quy mô lớn. Các trung tâm khoa học hỗ trợ đắc lực cho việc tăng năng suất cây trồng và vật nuôi, công nghệ sinh học được ứng dụng mạnh mẽ trong sản xuất nông nghiệp. Hoa Kì có số máy nông nghiệp đứng đầu thế giới, lượng phân bón sử dụng đạt 500 kg/ha.
Hoa Kì và Ca-na-đa là những nước xuất khẩu nông sản hàng đầu của thế giới. Mê-hi-cô có trình độ phát triển thấp hơn, nhưng đây cũng là một trong những nước đi đầu thực hiện cuộc Cách mạng xanh, đảm bảo được lương thực trong nước.

2^m+2ⁿ=2^m+n

=>2^m+2ⁿ=2^m.2ⁿ

=>(2^m+2ⁿ):2^m=2ⁿ

=>2^m:2^m+2ⁿ:2^m=2ⁿ

=>1+2^n:m=2ⁿ

Xét n=0=>2ⁿ=2⁰=1=1+2^m:n=>2^m:n=2=2¹=>m:n=1=>m=n=0

Xét n>0=>2ⁿ chia hết cho 2=>2ⁿ-1 không chia hết cho 2

=>2^m:n không chia hết cho 2

=>2^m:n=1=2⁰=>m:n=0=>m=0

=>2⁰+2^m=2^0.n

=>1+2ⁿ=2⁰

=>1+2ⁿ=1

=>2ⁿ=0

=>Vô lí

Vậy m=0,n=0

Một loài sinh vật có bộ NST lưỡng bội 2n. Thể một thuộc loài này có bộ NST là

A. 2n + 1

B. n + 1

C. 2n - 1

D. n - 1

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50.

Did you ever watch a video on the Internet? Maybe you used YouTube. YouTube is a Website

where people can share their video. Today, YouTube is an important part of the Internet. However, that wasn’t always true.

YouTube started with a young man named Jawed Karim and two friends. One day, Karim was on the Internet. He wanted information about the 2004 tsunami in Southeast Asia. He found news stories about it, but he couldn't find any videos. This gave Karin an idea. He wanted to help people put video on the Internet. Karim told his friends about this idea. Together, they created a company - YouTube.

YouTube become a global success. Millions of people around the world Visited the Website. It was clear to Google, another Internet company, that YouTube had a lot of value. Google made a deal. It bought YouTube for $1.65 billion. As a result, YouTube investors and its employees made a lot of money. The three friends who started YouTube were very big investors. Therefore, they made an enormous amount of money.

Karim became very rich, and he continued to work toward his PhD. There was something else he wanted to do. He wanted to help young people go into business. He used money and experience to start a new company called Youniversity Ventures. This company helps young people who have good business ideas. It gives them advice and money to start Internet businesses. Milo is one business that students started with the help of Youniversity Ventures.

Milo is a shopping Website. It helps people find products in stores near their homes. Another

example is AirBoB. This Web site helps people find for video conferences. People in different places can use this site to have business meetings.

Karim has some advice for students who want to start business. First, find a successful company. Do a lot of research about the company and the top people in the company. There, copy the way they do things. For students who wants to start Interner business, Karim is probably a very good example to copy.

Question 45: What do people use YouTube for?

A. doing shopping.

B. sharing Videos.

C. starting business.

D. finding vacation places.

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50.

Did you ever watch a video on the Internet? Maybe you used YouTube. YouTube is a Website

where people can share their video. Today, YouTube is an important part of the Internet. However, that wasn’t always true.

YouTube started with a young man named Jawed Karim and two friends. One day, Karim was on the Internet. He wanted information about the 2004 tsunami in Southeast Asia. He found news stories about it, but he couldn't find any videos. This gave Karin an idea. He wanted to help people put video on the Internet. Karim told his friends about this idea. Together, they created a company - YouTube.

YouTube become a global success. Millions of people around the world Visited the Website. It was clear to Google, another Internet company, that YouTube had a lot of value. Google made a deal. It bought YouTube for $1.65 billion. As a result, YouTube investors and its employees made a lot of money. The three friends who started YouTube were very big investors. Therefore, they made an enormous amount of money.

Karim became very rich, and he continued to work toward his PhD. There was something else he wanted to do. He wanted to help young people go into business. He used money and experience to start a new company called Youniversity Ventures. This company helps young people who have good business ideas. It gives them advice and money to start Internet businesses. Milo is one business that students started with the help of Youniversity Ventures.

Milo is a shopping Website. It helps people find products in stores near their homes. Another

example is AirBoB. This Web site helps people find for video conferences. People in different places can use this site to have business meetings.

Karim has some advice for students who want to start business. First, find a successful company. Do a lot of research about the company and the top people in the company. There, copy the way they do things. For students who wants to start Interner business, Karim is probably a very good example to copy.

Question 44: What does the word “This” in paragraph 2 refers to?

A. the 2004 tsunami in Southeast Asia.

B. that he could find no Videos.

C. the news stories he could find.

D. the information of the 2004 tsunami.