What do you do on the turn as your standard play with a 56/9/.5 - loose passive fish? Is this a check behind? What if the card was a 2?

PokerStars No-Limit Hold'em, $0.50 BB (6 handed) Poker-Stars Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

MP ($17)
CO ($54.70)
Hero ($58.35)
SB ($51)
BB ($35.40)
UTG ($19.45)

Preflop: Hero is Button with K, A.
UTG calls $0.50, 2 folds, Hero raises to $2, 2 folds, UTG calls $1.50.

Flop: ($4.75) T, 4, K (2 players)
UTG bets $1, Hero raises to $5.5, UTG calls $4.50.

Turn: ($15.75) T (2 players)
UTG checks, Hero bets $12, UTG folds.

Final Pot: $15.75