Stars 4/180 - JJ in early position, facing the A on the flop

[Tackleberry]

PokerStars No-Limit Hold'em Tourney, Big Blind is t50 (9 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

MP3 (t2910)
CO (t4805)
Button (t3970)
SB (t3715)
BB (t865)
Hero (t2330)
UTG+1 (t2235)
MP1 (t900)
MP2 (t1385)

Preflop: Hero is UTG with J[img]/images/graemlins/club.gif[/img], J[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">Hero raises to t150</font>, <font color="#666666">4 folds</font>, <font color="#CC3333">CO raises to t250</font>, <font color="#666666">3 folds</font>, Hero calls t100.

Flop: (t575) 3[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/diamond.gif[/img], 5[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">CO bets t250</font>, Hero ??

No real reads on Villain, because I joined the table just a couple of hands before.

Any help is greatly appreciated.

Thanks, Tackleberry.