根据句意及首字母提示补全单词。

1. —How long has your father been a doctor?

    —F_______ twenty years.

2. —What's your hobby?

    —I like c_______ stamps very much .

3. If you know the answer, please r_______ your hand.

4. "Jim skates well" means he is a good s_______ .

5. Sam has been skating s_______he was six