—How often do I need to feed the fish?

－They _______ food every day, or they will be hungry.

A．must give

B．mustn’t give

C．mustn’t be give.

D．must be given

在窗体上画一个命令按钮，然后编写如下程序：
Function fun(By Val num As Long)As Long
Dim k As Long
k=1
num=Abs(num)
Do While num
k=k * (num Mod 10)
num=num\10
Loop
fun=k
End Function
Private Sub Command1_Click()
Dim n As Long
Dim r As Long
n=InputBox("请输入一个数")
n=CLng(n)
r=fun(n)
Print r
End Sub
程序运行后，单击命令按钮，在输入对话框中输入"345"，输出结果为 【10】 。