

You are a specialist in playing 6-handed No Limit Texas Holdem. The following will be a game scenario and you need to make the optimal decision.

Here is a game summary:

The small blind is 0.5 chips and the big blind is 1 chips. Everyone started with 100 chips.
The player positions involved in this game are UTG, HJ, CO, BTN, SB, BB.
In this hand, your position is CO, and your holding is [Nine of Heart and Nine of Club].
Before the flop, CO raise 2.3 chips, and BB call. Assume that all other players that is not mentioned folded.
The flop comes King Of Spade, Seven Of Heart, and Two Of Diamond, then BB bet 2 chips, CO raise 8 chips, and BB call.
The turn comes Six Of Heart, then BB check.
You currently have One Pair(One Pair, Nines with King, Ten, Seven kickers).

Now it is your turn to make a move.
To remind you, the current pot size is 21.0 chips, and your holding is [Nine of Heart and Nine of Club]. You currently have One Pair.

Decide on an action based on the strength of your hand on this board, your position, and actions before you. Do not explain your answer.
Your optimal action is: