When I got home, my son _____. [ ]
A. has slept
B. have slept
C. was sleeping
D. slept
答案:C
力的作用效果,决定于力的______、______、______,叫力的______.
太阳经头痛,宜选用()
A.羌活
B.白芷
C.细辛
D.防风
E.荆芥