case后可以加a嘛？

in case后不可以加a

1.In case you should need any help, here's my number.萬一你需要幫助的話，這是我的電話號碼。

2.I have also taken out a life insurance policy on him just in case.為防萬一，我還給他買了一份人壽保險。

3.I'll stay around in case you need me.我就待在這兒，也許你用得著我。