— What should I do before operating the new machine?

— You’d better read its ______ first carefully.

A．explanations     B．instructions      C．descriptions      D．introductions

--- What should I do before operating the new machine?
--- You’d better read its ______ first carefully.

1. A.
   explanations
2. B.
   instructions
3. C.
   descriptions
4. D.
   introductions