压紧辊压力在保证管子在卷筒上不打滑的情况下，应（）以减轻管子间的挤压摩擦，防止产生扁管。
A.加大
B.不变
C.减小
参考答案：C
用所给的词的适当形式填空。
1. How much ______ (be) the blue socks?
2. Can you help ______ (I)?
3. She often ______ (watch) TV in the evening.
4. Can you ______ (buy) the shirt?
5. The yellow ______ (short) are $30.
灭活病毒无效的因素是（）.
A．干扰素
B．乙醚
C．青霉素
D．-70℃
E．紫外线
