I don't think ________ possible to master a foreign language without much memory work.

There were a lot of people in the park. We had ______ to take a rest, so we got very tired.

--Can I help you?  --I'd like to buy a present for my father's birthday, ___________ at a proper price but of great use.

I feel ____ is your husband who is to blame for the spoiled child.

You should make ______ a rule to leave things______ you can find them easily.