A.a=1,b=2
B.a=-1,b=2
C.a=1,b=0
D.a=-1,b=0
[单选题]A.a=1,b=2B.a=-1,b=2C.a=1,b=0D.a=-1,b=0
[单选题]( ).A.B.C.D.
[单选题]A.B.C.D.(1,2)E.(0,1)
[单选题]A.B.C.D.E.a