第一种合成塑料___________________.
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被成为塑料王的塑料是__________________.
热固性塑料指的是一种用加热方法固化的塑料。( )
A. 对
B. 错
所谓高分子材料指的就是塑料。( )
A. 对
B. 错
Could you help me repair my computer?---Sorry, Ihelp you. I am busy with my homework.
A. can't
B. mustn't
C. needn't
D. shouldn't