在图中画出平行于主光轴的入射光线经过透镜折射后的折射光线．
平行于主光轴的光线经凸透镜折射后将过焦点，如图所示；
外毒素
While prices are rising so fast, many people are working out ways to ______down their expenses.
A．cut
B．put
C．turn
D．settle
