Which is the correct tashahhud in prayer?

In the part where we do the tashahhud and raise the right hand index finger, which saying is correct (A) or (B)? : (A) Ash-hadu an laa ilaaha ill-Allaah wa ash-hadu anna Muhammadan rasooluh Allah (B) Ash-hadu an laa ilaaha ill-Allaah wa ash-hadu anna Muhammadan ‘abduhu wa rasooluh I always said it as (A) since I was young and I still do. But on the internet people say it as (B). Have I been saying it wrong? Does that mean all my prayers have been invalid?