科学的假设与猜想是科学探究的先导和价值所在．在下列假设（猜想）引导下的探究肯定没有意义的选项是（　　）

若函数f(x) (x∈R)是奇函数，函数g(x) (x∈R)是偶函数，则（   ）

根据句意和首字母提示完成下列句子。
There are sixty m____  in an hour．
He is ill, and his i____  makes us feel sad．
A lot of t____  are visiting the Great Wall, so it is very crowded．
Good food and e____  help me to study better．
It is n____ to eat a balanced diet.

一台电风扇，内阻为20Ω，接上220V电压后，消耗功率为66W，问：