脊髓灰质炎患者的传染性排泄物主要是（）

A.鼻咽分泌物

B.血液

C.粪

D.尿

E.唾液

He______the meeting, but upon learning that they would discuss something irrelevant to his field of study, he dropped the idea.

A．were going to attend

B．had attended

C．were to attend

D．would have attended