经血液循环传播的病原菌是（）
A.淋病奈氏菌
B.结核杆菌
C.葡萄球菌
D.链球菌
E.大肠埃希菌
参考答案：B
Beijing was attacked by such a terrible sandstorm ______few citizens had ever experienced before.
A．and it was
B．as
C．that
D．which
泥水盾构，在吸泥口前一般安置有搅拌器和（）。
A.切口环
B.螺旋输送机
C.阀门
D.格栅
