试题 试卷
题型：单选题 题类：常考题 难易度：普通
浙江省诸暨市牌头中学2017-2018学年高二下学期信息技术第一次月考试题
Private Sub Command1_Click()
Dim a As Integer
a = Val(Text1.Text)
Text1.Text = Str(Sqr(a))
End Sub
程序运行时，单击命令按钮command1后弹出如图所示的错误信息提示。出现错误的原因是（ ）
图1
实现上述功能的VB程序如下，请回答下列问题：
Dim a(20) As Long
Dim i As Integer, j As Integer, s As String List1.Clear
n = Val(Text1.Text)
a(1) = 1
List1.AddItem Str(a(1)) For i = 2 To n
s = ""
For j = Step -1
a(j) = ①
s = s + Str(a(j))
Next j
② Next i
试题篮
Step -1 
