Answer: c. Is the time to make a decision related to the quality of a player's hand.
Explanation: in a poker game the time to make a decisions is when "the clock has been called", at this time, the player has a limited amount of time to make a decision. So at this point his hand is termed a dead hands, and this can determine how professional a player is, if his hands keep focused and stable or shaking.
The best way she can record their performance using non-verbal cueing is by observing their hands when the clock has been called (that's the time to make a decision ).
So she can table her research to be "How stable the hand is at the time to make a decision, determines how professional the player is".