有如下VB程序段：

Dim a(1 To 5) As Integer, i As Integer, c As Integer

a(1)=2:a(2)=1:a(3)=3:a(4)=4:a(5)=5

c=0

For i=3 To 5

If a(i-2)+a(i-1)=a(i) Then c=c+1

Next i

Text1.Text=Str(c)

该程序段运行后，文本框Text1中显示的内容是（   ）

A、1

B、2

C、3

D、4