-- May I have a look?
-- __________.
A:Yes, I can.
B:Sure.
C:No, I'm not.
①若x,y∈C,则x+yi=1+i的充要条件是x=y=1;
②若a,b∈R且a>b,则a+i>b+i;
③若x2+y2=0,则x=y=0.