海伦•琼斯在《建筑与民主》中说:“……公民的权利与规模意味着政治是在公开场合进行的。而雅典人通常在雅典卫城西面的普尼克斯山半圆形的山坡上集会。……它的形状确保了每一个参加者不仅能看到发言的人,也可以看到其他出席的人。”此段描述( )
A:体现了雅典民主政治的开放性
B:反映了雅典分权与制衡的民主原则
C:折射出雅典民主政治的局限性
D:揭示了雅典民主法治的公正与客观
已知X是离散型随机变量,P(X=1)= 23 ,P(X=a)= 13 ,E(X)= 43 ,则D(2X﹣1)等于( )
①他将小球用一根细线悬挂起来,如图(a)所示,剪断细线后小球落下,如图(b)所示。
②他又将小球用两根细线悬挂起来,如图(c)所示,剪断其中的一根细线,小球发生摆动,如图(d)所示。通过实验,他的疑问得到解决根据实验现象及相关条件,小明同学归纳得出的初步结论:(选填下面对应的结论字母)
A:Can I help you?
B:____ I want to buy a sweater for my son.
A:We have sweaters in red, yellow and white. ____
B:Yellow.
A:Here you are.
B:Oh, this sweater is too small. ____
A:Yes. What about this one?
B:It's very nice. ____
A:It's ten dollars.
B:OK. I'll take it. ____
A:You're welcome.
A:Do you have a bigger one?
B:Thank you.
C:How do you spell it?
D:Yes, please.
E:What's your name?
F:What color do you want?
G:How much is it?