结核
参考答案：是岩石中的自生矿物集合体，这种集合体在成分．结构．颜色等方面与周围有显著不同。
I don't think throwing a big party is a bad idea. I love big parties. What's more, we should all our
friends who invited us to their parties. [ ]
A. pay off
B. pay for
C. pay back
D. pay out
（）检验一般有三种方式：首件检验巡回检验和完工检验。
A.进货
B.工序
C.成品
