The dictionary is of great use to me. I would gladly have paid       for it.

A．twice as much

B．twice as many

C．much as twice

D．many as twice

斑疹伤寒患者血清中可测出对变形杆菌“OX19”的抗体，是属于（）

A.间接凝集反应

B.直接凝集反应

C.反向凝集试验

D.交叉凝集反应

E.反向间接凝集反应