His father got him a job in a bank but soon it became clear ______ he was not fit for that kind of work．

A．why

B．what

C．whether

D．that

如图是小东同学正在为了让笔杆热起来伤脑筋呢!请你帮他出主意（给出两种原理不同的方法）。

（1）

① _______________________________________；

②________________________________________；

（2）两种方法的区别是__________________________。