The ______ to build up space stations on the Mars is, if we cannot say it is impossible, at least very hard to fulfill.

单选题

The question ______ now is where to build the new factory.

答案解析

单选题

The ______ to build up space stations on the Mars is, if we cannot say it is impossible, at least very hard to fulfill.

答案解析

单选题

The question_now is where to build the new factory.(5.0)(5.0)(5.0)

答案解析

单选题

How often ______ to the dentist?

答案解析

单选题

The children went there to watch the iron tower ______.

答案解析