A:Will you go shopping with us?
B:Are you going to have a talk with us?
C:I am going to swim.
已知向量a→,b→均为单位向量,若它们的夹角120°,则|a→+3b→ |等于 ( )
如图是小明设计的简易起重机的电路.下列操作中,电动机能工作的是( ).