Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.

It is the night of 5^th November that people in Britain light bonfires and have fireworks as a national tradition.

A. the night of 5^th November

B. in Britain

C. fireworks 

D. national 

Khối lượng CaF 2 cần dùng để điều chế 2,5kg dung dịch HF 40% (Biết hiệu suất phản ứng là 80%)

A. 1,95 kg.

B. 2,4375 kg.

C. 1,56 kg.

D. 4,88 kg.