— What do you think of the book?— Oh, excellent. It is worth ________ a second time.
The boy isn’t old enough ________ with the difficult problem by himself.
Not only Susan but also Sandy _________ abroad for traveling. They will return next Sunday.
— _________ has Liu Xiang taken part in world’s competitions of 110-metre hurdles?— I’ve no idea. Let’s find it out on the Internet.
After the earthquake, many kind-hearted people did what they could ________ those who suffered from it.
Japan and other countries have taken action ________ prevent nuclear radiation (核辐射).