PVC是（）聚合物。
A．聚丙烯
B．聚四氟乙烯
C．聚氯乙烯
D．聚苯乙烯
参考答案：C
She is not used to _______ like that.
A．speak to
B．spoke to
C．speaking to
D．being spoken to
何谓级配？通过级配试验可主要计算哪几个参数？
