

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 UTG, and your holding is [King of Diamond and Nine of Diamond].
Before the flop, UTG raise 2.0 chips, and BB call. Assume that all other players that is not mentioned folded.
The flop comes Seven Of Diamond, Six Of Club, and Four Of Heart, then BB bet 1 chips, UTG raise 5 chips, and BB call.
The turn comes Queen Of Spade, then BB check, UTG bet 18 chips, and BB raise 51 chips.
You currently have High Card(K-high).

Now it is your turn to make a move.
To remind you, the current pot size is 83.0 chips, and your holding is [King of Diamond and Nine of Diamond]. You currently have High Card.

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: