_____ how mirrors produce image, we need to know what light does. [ ]

Things that we’re facing should beconsidered ____，sothat we’ll deal with them well.

Great changes have taken place in that school. It is no longer ___ it was 20 years ago, ___ it was so poorly equipped.

You________scold such a pupil who always keeps silent so seriously that you________hurt him

We all miss the school we studied 3 years ago.