Up to now, Marin _____in the library for about two hours.
It’s bad for your eyes ____ computer games for a long time.
A policeman saw two thieves ____ a girl’s mobile phone on a bus and he caught them at once.
----Lily, keep the window ____. The sandstorm hasn’t stopped yet. ----OK, I’ll do that.
It was great fun _____ a picnic on the hill.
How long did you spend ____ your new house yesterday?