A. + =1

B. + =1

C. + =1

D. + =1

A.                          B.

C.                      D.

A.                                 B.

C.                             D.

A.=1                                           B.=1

C.=1                                       D.=1

若圆x²+y²=9上每个点的横坐标不变，纵坐标缩短为原来的，则所得曲线的方程是(    )

A. +=1                                            B. +=1

C. +y²=1                                           D. +=1