_______和________是病原体侵入人体后是否引起疾病的两个因素。
参考答案：病原体的致病能力；机体的免疫功能
His sister___________ her hometown for two years. She’ll return next year.
A．has been away
B．has left
C．has been away from
D．left
简述一下你了解的一部当代小说。
