Check/fold, bet/fold, or check/call on the river?

[Absolution]

One situation I often have difficulty with is knowing which of these 3 lines is the best on the river out of position with a marginal hand:

Check/fold
Bet/fold
Check/call

I'm not including bet/call and bet/raise because you generally have a hand too strong to fold in those situations. The situations I'm talking about are ones where, for example, you have a mid pair and the most likely draw hits on the river or someone has been calling the whole way. Most of the time I tend to default to bet/fold and I think a lot of others do as well because getting better hands to call + worse hands to call is generally better than getting better hands to bet + worse hands to check through + some percentage of bluffs to bet.


Here is an example:

The CO in this hand is generally loose passive, especially pre-flop, but can get aggressive post-flop, but I would say for the most part he is straight forward:

PokerStars 0.10/0.20 Hold'em (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Preflop: Hero is BB with 7[img]/images/graemlins/spade.gif[/img], Q[img]/images/graemlins/spade.gif[/img].
<font color="#666666">2 folds</font>, CO calls, Button calls, SB completes, Hero checks.

Flop: (4 SB) T[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/spade.gif[/img], 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, Hero checks, CO checks, Button checks.

Turn: (2 BB) 6[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, CO calls, Button folds, SB folds.

River: (4 BB) 2[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
Hero...

What's the best play here?