钢对含碳量的要求是（）
A．高于12%
B．高于1.7%
C．低于12%
D．低于1.7%
E．低于1%
参考答案：D
These days he has made _____ in his studies by working hard.
A．many progress
B．a lot of progresses
C．much progress
D．many a progress
资本资产定价模型适用于一切条件。（）
