VB中，mid（"A2B4"，2，1）的值是（）

A.dim str as string
B.dim str as string（256）
C.dim str as string[256]
D.dim str as string*256

A.if 50≤X≤200then y=1000
B.if x<=200andx>=50then y=1000
C.if x<=200orx>=50then y=1000
D.if x>=50，x<=200then y=1000

A.9
B.11
C.1
D.3