A:西周分封
B:春秋五霸
C:战国七雄
D:秦灭六国
读图,回答下列问题。
—Miss Gao has ____________ free time than Mr Green.—I think so. She is busy every day.
圆锥形烟囱帽的底面直径为80cm,母线长为50cm,则这样的烟囱帽的侧面积是( ).