下面VB程序段用二分查找的方法求不等式2^x+3x-5≤n(n≥0)的最大正整数解：

Dim left As Integer, right As Integer, n As Integer, x As Integer

n = Val(Text1.Text)

left = 1: right = n

Do While   ①   

    x = (left + right) \ 2

    If 2 ^ x + 3 * x - 5 <= n Then

        left = x + 1

    Else

        right = x - 1

    End If

Loop

Label1.Caption = "方程2^x+3*x-5<=n的最大正整数解为：" + Str(  ②  )

为实现程序功能，①②处代码应为（     ）

A、① left < right     ② left

B、① left < right     ② right      

C、① left <= right    ② left

D、① left <= right    ② right