若|a|=1,|b|=2,c=a+b,且c⊥a,则c与b的夹角为( ) A.30° 发布时间:2017-04-12 00:37 │ 来源:www.tikuol.com 题型:选择题 问题: 若|a|=1,|b|=2,c=a+b,且c⊥a,则c与b的夹角为( )A.30°B.60°C.120°D.150°
题型:选择题 —Your dress is very beautiful. —Thanks. This is _______ present that I got from my mother on my birthday. [ ]A. a B. an C. the D. / 查看答案