Anna is going on a tour of Van，and she wants to _______ Chinese history.

When ________ about one of the biggest problems today, many people say that an energy crisis is approaching and is threatening mankind’s survival[ ]

It was she that ________a sharp whistle, which makes ________possible for us to catch the thief.

Sorry I’m late. The first underground started moving __________ I could get on it.

na’s space technology has achieved____ breakthrough in this field, it really is ____ amazingwonder