40钢钢锭在1000℃左右轧制，有时会发生开裂，最可能的原因是（）
A.温度过低
B.温度过高
C.钢锭含磷量过高
D.钢锭含硫量过高
参考答案：D
合格焊缝的弯曲角度一般为（）。
A.120～180°
B.60～120°
C.90～180°
Since we have walked for two hours, let's stop ______. [ ]
A. to have a rest
B. have a rest
C. and had a rest
D. having a rest
