设A,B是集合{a1,a2,a3,a4,a5}的两个不同子集,
湖南龙山县里耶出土了大量的秦简,为研究汉朝的历史提供了珍贵的资料.(判断对错)
如图是一把折扇,∠O=120°,AB交CD∧于点E,F,已知AE=20,EF=4,则扇面(阴影部分)的面积为____ .
My father doesn't have much money. I don't have, ____.