All _____ can be done has already been done.

You don’t need to make fancy foods to impressguests—it is something simple but good _____ will do

The battery in my cell phone is running low.—- I _____ that last night before we went to bed.

Make a tentative guess _____ Peking Man_____ have done and used thousands of years ago

Some abstract modern paintings were ______ my understanding; I simply couldn’t figure out what the painters really wanted to tell us