Cho các phản ứng sau:

Số phản ứng sinh ra đơn chất là

A. 6

B. 3

C. 4

D. 5

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions. 

Ensure there is at least a 3cm space ______ allow adequate ventilation. 

A. so as to

B. so that

C. in view of

D. with a view to