What's wrong with your forehead（前额）？
I knocked my head on the tree while I _____my dog．（ ）
A．walkedB．was walking
C．has walkedD．am walking
We will visit the history Museum if it _______ tomorrow．（ ）
A．won't rainB．doesn't rain
C．wasn't raining
The telephone ______ by Alexander Graham Bell in 1876．（ ）
A．was inventedB．is invented
C．invented
Marcus is our foreign teacher．He _______ in our school for two years．（ ）
A．wasB．will beC．has been
Look!The man _____ be Mr．Black．He's always standing there at this time every day．（ ）
A．mustB．can'tC．mustn't
Going hiking with a group of people makes me _________．（ ）
A．relaxingB．to relaxC．relax