医院感染最常见的球菌是（）
A.金黄色葡萄球菌
B.A群链球菌
C.肺炎链球菌
D.脑膜炎奈瑟菌
E.淋病奈瑟菌
参考答案：A
Mr. Blake __________my letter, otherwise he would have replied by now.
A．will not have received
B．needn’t have received
C．shouldn’t have received
D．couldn’t have received
