慢性病原携带者作为传染源的主要意义取决于()

A．排菌量的大小

B．排菌时间的长短

C．活动范围的大小

D．职业和个人卫生习惯

Our English teacher wrote many notes about ______ English yesterday.[ ]

A. speak  

B. speaks  

C. to speak  

D. speaking