引起内源性感染的微生物来自于

A．肠道、口腔、呼吸道、 * * 、 * * 及皮肤等部位

B．人体内或体表的正常菌群或条件致病菌

C．医院的外环境

D．其他病人

E．医务人员

— Jenny took the 8:00 bus to Guangzhou this morning.

— Really? He _____ the 9:00 train. It's much more comfortable and safer to travel by train. [ ]

A. could have taken

B. should take

C. must have taken

D. can take