Nobody knows when the stone bridge ___ , because there is no record about it.
A. has built
B. was built
C. built
In some places trees ______ to stop the wind from blowing the earth away.
A. will plant B. planted C. are planted
When I knocked at the door , I heard her______ in the room .
A. sings B. singing C. to sing
Taiwan Island is______ the southeast of China.
A. in B. on C.to
There ______ the bell. It’s time for class.
A. goes B. comes C. gets
Bamboo（竹子）is made ______ pipes（管道）______ carrying water______ some farmers in the countryside.
A. by; for; into B. for; by; into C. into; for ; by