根据句意，写出括号内所给单词的适当形式。
____ Do you think it's good for you to keep worries to  _______ (your), boys and girls?
____ In China, it's becoming much _______ (hard) for people to pass the driving tests.
____ The government has realized the importance of the _______ (safe) of the children who take a school bus.
____ More and more teachers feel worried about some _______ (teenage) strange behaviour.

实验室中有一个热敏电阻R，其电阻值随温度变化的图象如图1所示．要测量热敏电阻在任意温度时的电阻值，现有下列实验器材：

一节旧干电池，两个开关S₁、S₂，导线若干．另外，还有再可供选择的以下器材：

A．电流表A（量程：0～0.6A，0～3A）；

B．电压表V（量程：0～3V，0～15V）；

C．定值电阻R₁（阻值：5Ω）；

D．定值电阻R₂（阻值：150Ω）．