The country has already sent up three unmanned spacecraft, the most recent          at the end of last March.

A．has been launched

B．having been launched

C．being launched

D．to be launched

汽车产品经过试销，汽车消费者对汽车新产品有所了解，汽车产品销路打开，销售量迅速增长的阶段是（）。

A.导入期

B.成长期

C.成熟期

D.衰退期