Serperior cannot learn any ghost type moves.
sentret and furret.
Sentret is a Normal type pokemon.
It is a ghost type move.
I don't know about Pokemon black and white, but in Generation IV the strongest ghost move is Shadow Force, but only Giratina can learn it. A decent ghost move is Shadow Ball if you can't get an Action Replay DS.
A ghost type move.
With a ghost or dark type move.
There is no Ghost Pokémon that can learn Helping Hand.
Sentret is #161 in the national pokedex, and it is a Normal type Pokemon.
yes his name is saleaf
Yes, there are many Normal-type Pokemon that can learn Shadow Ball, among other Ghost-type moves, by TM. This is useful for beating Ghost-type Pokemon, since Normal-type Pokemon are immune to Ghost-type attacks.
misdreavus can learn dark, ghost, psychic and thunder type move. like shadow ball, thunderbolt, psybeam, and spite. pain split is the move that only misdreavus will be able to learn. -it is a move that cut's the hp of the opponent through the pain you have, and the hp that was cut was added to yours.