在如图Ⅱ-4所示的锅炉总图及炉墙总图中，表示窥视孔的是（）
A.选项A
B.选项B
C.选项C
参考答案：B
- Mum, can I help you with the cleaning?
- Thank you, dear. But you are _______ now. You must wait until you are _______.
A．too young; too old
B．too young; enough old
C．so young; enough old
D．too young; old enough
试述游泳活动对中老年人的益处。
