单项选择题

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")
Setfd=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