If you do not know how to ____you at table in a foreign country, you should copy the host.

My teachers try their best ______ our problems.

(2013·陕西西北工大附中一模) ________ a little earlier, you could have got a copy of his latest book.

Recent campus tragedies show thatsafety measures are so important that we _______ take them too seriously.

_____ work has been done to improve our living environment.