For tournament play, this:
B. Deal his spot, put in his blinds when necessary, and auto-muck his cards.
The dealer mucks the absent player's hand once dealing to all players is completed and before first action by the UTG player (who then has knowledge of an undefended blind, as does all other players).
For cash games, it totally depends on house rules, and in most cases, how long the player is absent. Usually one of the two shown below, but certainly not limited to just these rules:
Absent players are not dealt cards and do not post blinds, and must pay any missed blinds immediately upon return (if one orbit or less) or wait until the button has passed to resume play. The actual RROP rules state:
- A player who misses any or all blinds can resume play by either posting all the blinds missed or waiting for the big blind. If you choose to post the total amount of the blinds, an amount up to the size of the minimum opening bet is live. The remainder is taken by the dealer to the center of the pot and is not part of your bet. When it is your next turn to act, you have the option to raise.
- If a player who owes a blind (as a result of a missed blind) is dealt in without posting, the hand is dead if the player looks at it before putting up the required chips, and has not yet acted. If the player acts on the hand and plays it, putting chips into the pot before the error is discovered, the hand is live, and the player is required to post on the next deal.
-OR-
Absent players are dealt cards and blinds are posted when required. The dealt hand is live until facing action, at which point it is ruled dead if the player is not present (or 'on-the-way' by way of announcement). Typically this is only done for the first orbit, at which time the player is no longer dealt cards and is not required to post blinds until they return.
The latter is probably the more common of the two, and is what
@DrStrange cited above. I like his option of letting another player play the abandoned hand blind if so inclined (assuming that the other player doesn't otherwise already have live cards in the hand).