用括号中所给的单词的适当形式填空，每个单词限用一次。

(busy   swim   hard   three   ourselves)

1. Father's day is on the _________ Sunday in June.

2. The traffic during the rush hour is much _________ than usual.

3. We must learn to look after __________ when we are alone at home.

4. _________ is good for health.

5. When I got to the top of the high mountain, I could __________ walk any more.