He said ______ couldn’t he work out the problem but his teacher didn’t know how to do it

The group’s research has done much toourknowledge of the HIV virus

were many people standing by, but _____ of themwere willing to help the poor boy.

Why does Mr Black look so sad this morning?—I hear that a fire________in his house and lots of valuable things were burned last night.

下列各句中，没有语病的一句是(　　)