Not until ________ school ________ how much their teachers loved them and helped them．

A．they left, they realized

B．did they leave, did they realize

C．they left, had they realized

D．they left, did they realize

________ a written permission, he had to write another letter to the president of the university．

A．Not giving

B．Not having been given

C．Having not given

D．Having not been given

________ a diary every day, and you'll improve your writing．

A．Keeping

B．To keep

C．Keep

D．If you keep

Low-carbon lifestyle is of great benefit to improve the world environment．________ can be enjoyed from it until you have a deep understanding of it, however．

A．Something

B．Nothing

C．Few

D．Much

In Copenhagen Climate Conference, rich countries promised to ________ a fund of ＄100 billion a year by 2020 to help developing countries．

A．make up

B．put up

C．set up

D．send up

Every country has the responsibility to ensure a safe, ________ and healthy development of the nuclear energy．

A．flexible

B．reliable

C．available

D．acceptable

We should realize that there are other things that society should value besides high marks, ________ honesty and responsibility．

A．for example

B．namely

C．such as

D．that is

Too high house prices can be brought under control, ________ the authorities introduce a series of regulatory policies．

A．even if

B．as if

C．so that

D．provided that

If we had taken such effective measures much earlier, the river ________ so seriously now．

A．is not polluted

B．would not be polluted

C．had not been polluted

D．would not have been polluted

________ a small house in the distance．Let' go to see if there's someone living in it．

A．It seems

B．It seems to be

C．There seems to have

D．There seems to be