PokerStars No-Limit Hold'em, $1.00 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

Hero ($131.50)
CO ($128.30)
Button ($69.85)
SB ($101.95)
BB ($150.75)
UTG ($46.15)

Preflop: Hero is MP with A, J.
1 fold, Hero raises to $3.5, CO calls $3.50, 3 folds.

Flop: ($8.50) 9, 2, K (2 players)
Hero bets $5.5, CO calls $5.50.

Turn: ($19.50) A (2 players)
Hero ???

---

Villian is 45/6/.4 over 46 hands.

What's your play on the turn?