wonder how it ________ that they made such rapid progress.

Sorry , Mr. Green, I _______ my note book at home.–That’s OK, but don’t forget it next time.

Once a year, people take part in “_______ Lights” activity to help save energy.

How do you study for a test— workingwith friends.

It’s too complex，I think—______So we’d better make it easier for students to get involved