窗体中有文本框Text1、Text2和Text3。运行,输入整数m和n(n>0),单击按钮Command1计算下列表达式的值: SUM=m-(m+1)/2+(m+2)/3-(m+3)/4+...+(-1)n+1(m+n-1)/n 在Text3给出结果,事件代码如下: Private Sub Command1_Click() Dim sum As Double m=Val(me!Text1) n=Val(me!Text2) sum=0 For k=1 to n sum=sum+【 】/k Next k Me!text3=sum End Sub 程序【】处应填写的语句是( )。 A. IIf(k Mod 2 = 0, -(m + k - 1), (m + k - 1)) B. IIf(k Mod 2 = 0, (m + k - 1), -(m + k - 1)) C. IIf(k Mod 2 > 0, -(m + k - 1), (m + k - 1)) D. IIf(k Mod 2 < 0, (m + k - 1), -(m + k - 1))