He spends two hours _________ exercise every day.[ ]
A. doing
B. do
C. to do
D. does
答案:A
羊狂蝇的发育不包括()
A.第一期幼虫
B.第二期幼虫
C.第三期幼虫
D.虫卵
E.蛹
呼吸衰竭