随着居民收入水平的提高，食品支出比重的变化趋势是（）
A.逐步下降
B.逐步上升
C.先下降后上升
D.先上升后下降
参考答案：A
The boy told us______. [ ]
A. that he has collected 200 stamps
B. that he had collected 200 stamps
C. if he has collected 200 stamps
D. if he had collected 200 stamps
性交后精子穿透力试验的最佳时间是
A．经净后3日B．月经来潮前3日C．预测排卵日D．两次月经中间E．非经期的任何日期
