单项选择题

下列程序段执行时在屏幕上显示的结果是
x1=40
x2=60
SET UDFPARMS TO VALUE
DO test WITH x1, x2
x1, x2
PROCEDURE test
PARAMETERS a, b
x=a
a=b
b=x
ENDPRO

A) 60 60
B) 60 40
C) 40 40
D) 40 60