Công thức một đoạn mạch của tơ nilon-6 là:

A. (-CH₂-CH=CH-CH₂)_n

B. (-NH-[CH₂]₆-CO-)_n

C. (-NH-[CH₂]₆-NH-CO-[CH₂]₄-CO-)_n

D. (-NH-[CH₂]₅-CO-)_n

Cho phát biểu đúng là

A. Tơ olon thuộc tơ tổng hợp.

B. Tơ olon thuộc tơ poliamit.

C. Tơ olon thuộc tơ nhân tạo.

D. Tơ olon thuộc tơ thiên nhiên.

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions.

They were late for the meeting because of the heavy snow.

A. If it snowed heavily, they would be late for the meeting. 

B. Had it not snowed heavily, they would have been late for the meeting. 

C. But for the heavy snow, they wouldn't have been late for the meeting. 

D. If it didn't snow heavily, they wouldn't be late for the meeting.