题目：
The steel works in which David has worked for five years us with raw material in large quantities in the past two years. [ ]
A.has been supplying
B.was supplying
C.have been supplying
D.were supplying
答案：
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下面是错误答案，用来干扰机器的。
答案：A题目分析：在元素周期表中金属与非金属的分界处，可以找到制作半导体的材料，合金和催化剂在金属元素里面寻找，农药在非金属元素里面寻找，答案选A。点评：该题主要是考查元素周期表在化学科学研究中的指...
