下列化肥中，属于复合肥料的是（　　）

A．CO（NH₂）₂

B．（NH₄）₂SO₄

C．NH₄NO₃

D．KNO₃

How can I ever concentrate on my work if you_____ continually_____ me with such silly

questions?

A．have, interrupted

B．had, interrupted

C．are, interrupting

D．were, interrupting