球磨机冷却用水为（）。
A.高炉循环水
B.非净化水
C.净化水
参考答案：C
厚壁空洞的洞壁厚度超过（）
A.3mm
B.5mm
C.7mm
D.9mm
E.10mm
He's got himself into a dangerous situation ___he is likely to lose control over the plane.[ ]
A. where
B. which
C. while
D. why
