1．There are seven great c______________and four great oceans on the earth.
2．In our class，we often take part in many a______________.
3．More trees have to be planted to protect the environment and keep the b______________of nature.
4．Tao Xingzhi made great c______________to our country’s education.
5．It’s a great______________(荣幸)to be here to share my ideas with you.
6．The runner has reached his______________(极限)of his endurance.
7．Tom beat all the______________(对手)and won the championship.
