螺钉旋具选用时首先考虑的是（）。
A、旋柄材料
B、螺钉长度
C、螺钉头部沟槽形状
D、旋杆长度
参考答案：C
控制除盐系统进水中的COD含量，主要是防止树脂受（）污染。
It was from only a few supplies that she had bought in the village _____ the hostess cooked such a nice dinner. [ ]
A. where
B. that
C. when
D. which
