As the city has become increasingly ______
题型：单项选择题
问题：
As the city has become increasingly ______ and polluted, there has been a growing realization that certain action urgently needed.
A. flourished B. boosted C. congested D. mingled
题型：单项选择题
如图所示，一束截面为圆形（半径R）的平行单色光垂直射向一玻璃半球的平面，经折射后在屏幕P上形成一个圆形亮区．已知玻璃半球的直径为d=0.1米，屏幕p至球心的距离为s=0.4米，不考虑光的干涉和衍射，若玻璃半球对单色光的折射率为n=
，求圆形亮区的半径．2
