There are nine______ students at Green High School. Five _____ of them walk to school.

It was a cold winter night, and there wasn’t anyone __________the boy could turn for help in the street.

He didn’t listen to the teacher carefully., he couldn’t answer those questions.

________you _____your homework yet? —Yes, I ___it ten minutes ago.

Must I turn off the gas after cooking? —Of course, you can never be ____careful with that．