1. The Smith family are inscrutable folks. They don't like to be around other people. When they are around others they never speak.2. Math is so hard to me.3. Physics is hard to understand.
 inscrutable hard to understandinscrutable 可用在難懂的事物上面< >
She is shy, but when there is a guest at home, she becomes excted and hyperactive and out of control.