—Where are the guests to be from tomorrow?

—Many an American boy and many a British girl as well as the teachers to he present.

A．have been invited

B．has been invited

C．were invited

D．was invited

导致输卵管妊娠的常见原因是（）

A.慢性盆腔炎

B.输卵管黏膜炎和输卵管周围炎

C.输卵管切除术后

D.输卵管过长

E.放置宫内节育器