下列电路图,开关S闭合后,两个电阻串联的是
A:A
B:B
C:C
D:D
____ ____you know that girl. She's in your class.
已知点G是△ABC的重心,AG→=λAB→+μAC→λ,μ∈R若∠A=120°,AB→·AC→=-2,则AG→的最小值是( )