If people from different countries learn to respect each other’s customs and cultures, our world will sure to become a big happy family ______.

A. some time            B. some day              C. some times                             D, sometimes

放映的映前准备有哪几项？（）

A.放映机的清洁与润滑

B.放映前的外部检查

C.放映设备的通电检查

D.影片的检查