no reads. awful turn play. bet river?

Full Tilt Poker No-Limit Hold'em, $0.25 BB (9 handed)

Button ($19.20)
SB ($5.50)
BB ($24)
Hero ($45.45)
UTG+1 ($8.95)
MP1 ($10.40)
MP2 ($62.75)
MP3 ($14.75)
CO ($24.65)

Preflop: Hero is UTG with [Ad], [Ks].
Hero raises to $0.75, 2 folds, MP2 calls $0.75, MP3 calls $0.75, 1 fold, Button calls $0.75, 1 fold, BB calls $0.50.

Flop: ($3.85) [Qh], [4s], [As] (5 players)
BB checks, Hero bets $3.25, MP2 calls $3.25, MP3 folds, Button folds, BB folds.

Turn: ($10.35) [4c] (2 players)
Hero bets $4, MP2 calls $4.

River: ($18.35) [5h] (2 players)
Hero ??