穿过英国伦敦格林尼治天文台旧址的0°经线是( )
A:北极圈
B:北回归线
C:本初子午线
D:赤道
-It's important for us to know _________ all the subjects. -Yeah, group work is my favorite.
已知a→=1,2,b→=x,1且a→+2b→∥2a→-b→,则x为 ( )