1 . “Solving ________ problem of plastic pollution is important. Landfill space is becoming limited,” says Wu, a Stanford University environmental engineering instructor. (用适当的词填空)

2 . Chinese hamburgers are very real and they predate ________ hamburgers we call our own in the U. S. (用适当的词填空)

3 . Our National Day is on ________ first day in ________ October.

A．a; the

B．the; a

C．the; /

D．a; /

4 . Much to our delight，the sound of water in ________ distance caught our attention and drove us to the river bank. (用适当的词填空)