病毒性肝炎时,肝细胞损伤取决于()。
A.T细胞介导的细胞免疫反应
B.免疫复合物介导的超敏反应
C.迟发性免疫反应
D.病毒的直接损伤
E.机体免疫反应的强弱
参考答案:A, D, E
Tom ______ swimming for 3 hours, and his son ______ an hour ago. [ ]
A. has started; has started
B. have started; has started
C. started; started
D. has been; started
复飞电门位于哪个油门杆上?
A、左
B、右
C、左和右