—Has your father returned from Africa yet?—Yes,but he _______ here for only three days before his company sent him to Australia.

(2013·高考新课标全国卷Ⅰ)If we________now to protect the environment，we’ll live to regret it.

With more forests being destroyed in that area, huge quantities of land _______ deserts each year.

A single pipeline ___________ all the houses with water.

It was snowing hard and Mother told me to put on a thick coat to ______myself from the cold.