题目

有如下VB程序段： Dim i As Integer, sum As Integer Dim a(1 To 6) As Integer, b(1 To 6) As Integer sum = 0 a(6) = 18: a(5) = 7: b(6) = 14: b(5) = 16 For i = 4 To 1 Step -1a(i) = a(i + 2) - a(i + 1)b(i) = b(i + 2) - a(i)If b(i) Mod 3 = 0 Then sum = sum + b(i) Next i Text1.Text = Str(sum) 该程序段运行后，文本框Text1中显示的内容是（ ） A . 39 B . 30 C . -9 D . 12网络时代的到来，很多家庭都拉入了网络，一家电信公司给顾客提供上网费的两种计费方式：方式A以每分钟0.05 元的价格按上网时间计费；方式B除收月基费54元外加每分0.02元的价格按上网时间计费．如何选择更经济？