用单词的适当形式填空。

1.  He didn't go to school because of his ______ (sick).

2.  The old man is______ (serious) sick, he is much ______(sick) than yesterday.

3.  He runs much  _____ (fast) than his brother.  He runs______  (fast)in his class.

4.  Here ______(be) some of the results.

5.  Do you think cars are ______(safe) than bikes?