--- Where is your mother?

--- She has ______ to Sichuan on business. She has ______ there four times recently.

A．gone, gone

B．been, been

C．gone, been

D．been, gone

关于沙门菌属食物中毒，叙述不妥的是()

A．患者带菌时间短，不是主要传染源

B．传染源是家畜、家禽和鼠类

C．病原体存于动物的肠腔和内脏

D．进食被沙门菌污染的内脏，肉、蛋类受感染

E．发病的原因是由于食入大量的毒素而不是活菌