PokerStars No-Limit Hold'em, $0.50 BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

SB ($203.80)
BB ($14.55)
UTG ($27.85)
Hero ($52.25)
Button ($9.50)

Preflop: Hero is MP with 9, 9.
1 fold, Hero raises to $2, 1 fold, SB calls $1.75, 1 fold.

Flop: ($4.50) 5, 6, 5 (2 players)
SB checks, Hero bets $3.5, SB calls $3.50.

Turn: ($11.50) K (2 players)
SB bets $8, Hero ???

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Villian is 26/8/2.4 over 50 hands.

What's your move on the turn?