8．You must put the piano there，with its back a_______ the wall．

7．Everyone should stop p______ the Bailang River，instead of putting waste into it．

6．The Chinese scientists did many scientific e______ before they sent the Chang’e-1(嫦娥一号) into space．

5．People learn languages to _________(沟通)with others．

4．The pandas live in the ______________(自然)reserve．

3．Planting trees can help to make our _________ (环境)clearer and more beautiful．

2．The ___________ (高度)of the Mount Tai is about 1,532 meters．

1．Mrs．Smith smiled ___________ (幸福)when she received the present on Mother’s Day．