用括号内所给单词的适当形式填空。

1.  Thomas Edison was a great American            (invent).

2.  We have            (fly) on the plane for two hours.

3.  You must keep the child away from the           (boil) water.  It is dangerous.

4.  I want to play on China s           (nation) basketball team some day.

5.  I think it's very uncomfortable to wear high            (heel) every day.

( )是指保证人以自己的名义作为一方当事人的关系人，向另一方当事人作履行合同担保的一种方式。

A．定金

B．留罩

C．保证

D．质押