1.Someone called Fred is going to call you,aren't you?

1.Someone called Fred is going to call you,aren't you?
反义疑问句,为什么后面用aren't you?
2.A:Shall me sing Karaoke at the party?
B:XXX.
a) Yes,I'd love to.b)All right.I'll do that.
c) Yes,that's a good idea d)Thank you,the same to you.
为什么该题选择c),而不选择a)?
Sorry,第2个提问的题干是 Shall we 而不是Shall me