Subway Line 4，into use in September 2009，has made traveling in Beijing easier．

In his book,he explains both ______ it means to be a scientist and ______ science works.

Have you heard that Tom was given a good beating by his father last night? – He __________ it. He was making trouble everywhere all the time.

I don’t think they will help us, ?

There must have been a large number of tourists in Sanya during the past Spring Festival, __________?