_______ very high speed, the rocket rushed into the air and soon disappeared.

A．With

B．By

C．At

D．On

在窗体上添加一个命令按钮，然后编写如下事件过程：
Private Sub Command1_Click()
sum=0
For i=3 To 7
sum=i+2
Next i
MsgBox sum+i
End Sub
打开窗体后，单击命令按钮，消息框的输出结果是______。