The art club is for members only. You can’t go in _______ you are a member.
There is _____pollution and ____fishes in the river now than 20 years ago.
The sign(标志牌)made us safe.
Everyone should play a part in _____the earth.
-- ________ will Mr. Green be back? -- In a week, I think.
It's easy ______ a banana milk shake. Let me help you.