内部故障成本包括（）。
A.废品损失
B.退货损失
C.产品降价损失
D.停工损失
E.返修损失
参考答案：A, D, E
247. He found it quite impossible to learn _____ well in less than 6 months so he registered for the next semester(term).
A．Russian
B．Russians
C．Russia
D．Russias
统一作用
