在一个边长为40米的正方形水池边种树，每隔5米种一棵，一共种树多少棵？
9×4-4=32（棵）
Although my grandfather is in his eighties, he is still as ________ as a young man and hates sitting around doing nothing all day.
A．enthusiastic
B．intelligent
C．energetic
D．sensitive
人体浸于水中的安全电压为（）V。
A、50
B、36
C、25
D、2.5
Although my grandfather is in his eighties, he is still as ________ as a young man and hates sitting around doing nothing all day.