---Where did you find our chemistry teacher? ---It was in the lab he was doing his experiment.
I still remember that terrible accident a few days ago, ____ more than 20 pupils were killed.
The police said they would not give up looking into other possibilities ____they find out what happened.
When Justin didn’t ____ for lunch the next day, Mrs Foster became worried and called the police.
If ____ in, the viruses can result in illness or even deaths.
Standing inside ____ lots of strange creatures with white skin and large black eyes.