Only 16 percent of China’s area ____ covered with forests, so ____of us should protect trees. 

My mother asked me if ______________ a picnic the next week in our school.

Three-fourths of the buildings ______.

I hear a number of workers in the factory_____out of work.__Yes, and the number _____quite huge.

—Does the old man know the museum very well? —No, this is the first time he __________ here.