Ten minutes had been made full ____ of ____ the problem.

A．using; studying

B．use; to study

C．to use; to study

D．use; studying

我国发展对外经济关系的基础和主要内容是

A．发展对外贸易

B．有效地利用外资

C．开展对外技术交流

D．实施“走出去”战略