How kind you are! You always do what you can ________ me.

---How did you work out the difficult chemistry problem?
--- I worked it out by ________.

The singer sang many songs, ________ some of my favorites.

The book is very difficult. ________ read something easier?

Don’t forget ______ the door when you leave.

It’s easy ______ English and it’s important ______it.

When shopping, keep your eyes ______for those energy-saving machines.

It’s very not outside.  Why don’t you stay at home?

— It is so hot in the classroom. Would you mind ____ the windows?
—OK. I’ll do it right now.

It’s necessary        us        English well.