Be sure _______ when you enter the cave. Otherwise, you’ll hit your head on the rocks.

We all know that a smile is usually a sign ________ people feel friendly and happy.

Stage fright is a common example of ______educators call a “lack of confidence” among students

r your instruction, I ______ such great progress in so short a time. Thanks a lot.

The boots are _____ designed and they can prevent us from _____ in the air.