波长小于400nm的光称为（）。
A.紫外
B.红外
C.可见光
D.紫外+可见光
参考答案：A
She asked me if I knew ______ . [ ]
A. whose pen is it
B. whose pen it was
C. whose pen it is
D. whose pen was it
煤矿井下低压供电系统“三大保护”是指________保护？
