选择题   采用DAO完成对“教学管理.accdb”文件中“学生表”的学生年龄都加1的操作，程序空白处应填写的语句是______。
    Sub SetAgePlus()
    Dim ws As DAO. Workspace
    Dim db As DAO. Database
    Dim rs As DAO. Recordset
    Dim fd As DAO. Field
    Set db=CurrentDb()
    Set rs=db. OpenRecordset('学生表')
    Set fd=rs. Fields('年龄')
    Do While Not rs. EOF
    ______
    fd=fd+1
    rs. Update
    rs. MoveNext
    Loop
    rs. Close
    db. Close
    Set rs=Nothing
    Set db=Nothing
    End Sub