The citizens didn't feel safe at all after several families had their house（）sat night and a lot of things stolen.

A．broken in

B．broken into

C．to be broken into

D．break in

环状沉淀试验中要求（）

A.抗原澄清

B.抗原和抗体都必须澄清

C.抗体澄清

D.对抗原和抗体没有特别要求

E.抗原可以不澄清