用所给单词的适当形式完成句子。

1. The old man often makes a _         (speak) in our school.

2. The chairman looked _         (ordinary) than we thought.

3. Playing games online is              (harm) to your study.

4. Many scientists are trying to explain the               (disappear) of the dinosaurs.

5. Although I am your friend, I _          (agree) with your wrong idea.