Cho 18,5 gam chất hữu cơ A (có công thức phân tử C₃H₁₁N₃O₆) tác dụng vừa đủ với 300ml dung dịch NaOH 1M tạo thành nước, một chất hữu cơ đa chức bậc I và m gam hỗn hợp muối vô cơ. Giá trị gần đúng nhất của m là

A. 19,50

B. 25,45.

C. 21,15.

D. 8,45.

Read the passage and choose the best answer.

A pilot cannot fly by sight alone. In many conditions, such as flying at night and landing in dense fog, a pilot must use radar, an alternative way of navigating. Since human eyes are not very good at determining speeds of approaching objects, radar can show a pilot how fast nearby planes are moving. The basic principle of radar is exemplified by what happens when one shouts in a cave. The echo of the sounds against the walls helps a person determine the size of the cave. With radar, however, the waves are radio waves instead of sound waves. Radio waves travel at the speed of light, about 300,000 kilometers in one second. A radar set sends out a short burst of radio waves. Then it receives the echoes produced when the waves bounce off objects. By determining the time it takes for the echoes to return to the radar set, a trained technician can determine the distance between the radar set and other objects. The word “radar”, in fact, gets its name from the term “radio detection and ranging”. “Ranging” is the term for detection of the distance between an object and the radar set. Besides being of critical importance to pilots, radar is essential for air traffic control, tracking ships at sea, and for tracking weather systems and storms. 

 The word “shouts” in the passage most closely means _______.  

A. “exclaims”

B. “yells” 

C. “shoots” 

D. “whispers”

Mark the letter A, B, C, or D on your answer sheet to complete the sentence.

John: “Do you think that we should use public transportation to protect our environment?”
Mary: “____________”

A. Well, that’s very surprising

B. Yes, it’s an absurd idea

C. Of course not. You bet!

D. There’s no doubt about it.

Mark the letter A, B, C, or D on your answer sheet to indicate the word or phrase that is CLOSEST in meaning to the underlined part in each of the following questions

I will communicate with you as soon as I have any news

A. be interested in                   

B. get in touch               

C. have connection                  

D. be related