男性，36岁，患者呕血不止，烦躁，出冷汗。
曾有胃溃疡史，呕血的原因可能为
A．胃溃疡
B．胃癌
C．慢性胃炎
D．十二指肠球溃疡
参考答案：A
He tried his best to solve the problem , ______difficult it was. [ ]
A. however
B. no matter
C. whatever
D. Although
钢球磨煤机检修后试转，当主轴承温度大于（）℃时为不合格。
A.40
B.50
C.60
