________ you stepped into the lab with your shoes on? You’re supposed to take them off before you enter it. I told you so!
The area ______ the explosion happened was closed off by the police.
She had a bad cold, but luckily began to _______ soon.
Everyone was trying to ________ a better idea to persuade him to stay.
Use your head, _______you’ll work out the problem.
_______ is known to all, Lu Xun was famous as a great thinker.