QQ bet or check this river?

[LuckyDevil]

Simple question. Should i bet or check on this river?

MP2 is unknown and CO is 28/5/1.3.

Party Poker 2/4 Hold'em (10 handed) converter

Preflop: Hero is MP3 with Q[img]/images/graemlins/heart.gif[/img], Q[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">4 folds</font>, MP2 calls, <font color="#CC3333">Hero raises</font>, CO calls, <font color="#666666">3 folds</font>, MP2 calls.

Flop: (7.50 SB) 7[img]/images/graemlins/spade.gif[/img], 9[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
MP2 checks, <font color="#CC3333">Hero bets</font>, CO calls, MP2 calls.

Turn: (5.25 BB) 6[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
MP2 checks, <font color="#CC3333">Hero bets</font>, CO calls, MP2 calls.

River: (8.25 BB) K[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
MP2 checks, Hero ????

Final Pot: 8.25 BB