A:12
B:−12
C:2
D:﹣2
Private Sub Form_Click( )
Dim x as Integer, n as Integer
x=1
n=0
Do While x < 20
n=n+1
x=x * 3
Loop
Text1.Text=Str(x)
Text2.Text=Str(n)
End Sub
气体制备时须先检查装置的气密性.如图所示,表明装置漏气的是( )