A.x²+y²=3           B.x²+y²=         C.x²+y²=9            D.x²+y²=1

A.                                  B.或

C.2kπ+(k∈Z)                         D.kπ+(k∈Z)

A.1                 B.-1               C.1或-1              D.不确定

A.第一象限                            B.第二象限

C.第三象限                            D.第四象限

A.x=0且y=3                           B.x=0且y=-3

C.x=5且y=3                           D.x=3且y=0