---What ____ the population of China ? ---China has a population of 1.3 ____.
According to the record reports, one of the rare animals, ______ crocodile, is in ______ danger of dying out.
______, ______ many boys, Jack like playing football.
This is the ____ piano on which the composer created some of his greatest works.
Perhaps we need to clear away these books to make ______ for our new students.
The police have finally ______ the mystery (疑案).