River check or bet

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Paradise Poker 40/80 Hold'em (6 handed) FTR converter on zerodivide.cx

Preflop: Hero is CO with A[img]/images/graemlins/diamond.gif[/img], 6[img]/images/graemlins/diamond.gif[/img]. Hero posts a blind of $40.
UTG calls, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero (poster) raises</font>, <font color="#666666">1 fold</font>, SB calls, BB calls, UTG calls.

Flop: (8 SB) A[img]/images/graemlins/club.gif[/img], 8[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, BB checks, <font color="#CC3333">UTG bets</font>, Hero calls, SB calls, BB folds.

Flop: Call as opposed to raise partly because the flop contains very few draws, partly because my kicker is weak, and partly just to mix up my play.

Turn: (5.50 BB) 7[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, <font color="#CC3333">UTG bets</font>, <font color="#CC3333">Hero raises</font>, SB folds, UTG calls.

Turn: having picked up so many draws, it seems clear to raise.

River:(9.50 BB) T[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
UTG checks, Hero ?????

River: A lot of people would have just called my turn raise with hands like AT, AJ, AQ. Also opponent could have made two pair on the end.

On the other hand it is also possible they have a hand like 89, 99, etc.

Thoughts?