单项选择题

下列程序执行后,变量x的值为( )。 Dima,b,c,d As Single Dim x As Single a=100 b=20 c=1000 Ifb>a Then d=a:a=b:b=d End If Ifb>c Then X=b Elseif a>c Then x=c Else x=a End If

A.100
B.20
C.1000
D.0