有如下程序段：

a(1)=False

For i = 2 To 20

a(i) = True

Next i

For i = 2 To 20

If a(i) = True Then

For j = 2 To 20 \ i

 a(i * j) = False

Next j

End If

Next i

t = 0

For i = 1 To 20

If a(i) = True Then

t = t + 1

End If

Next i

经过该程序段运行后，变量t的值为（   ）

A：5

B：6

C：7

D：8