Alice _____ ill, for she didn.t come to the class yesterday.
A．was
B．had been
C．must have been
D．should have been

参考答案：C 答案解析： for前多加逗号，一般是对结果作出推断性的补充说明或解释，不表示直接原因，这里用must have done意为“一定是做了某事”，用should have done意为“过去本应该做某事，而实际未做”，所以这里应该是猜测Alice一定是病了，因为她昨天没有来上学，故选择C。