Which of the following property is used to define the time it takes one iteration of an animation to play?

The correct answer is: C. transition-duration

The transition-duration property is used to define the time it takes one iteration of an animation to play. It is a CSS property that specifies the duration of a transition effect. The value of the transition-duration property is a length value that specifies the number of seconds or milliseconds that the transition should take.

The other options are incorrect because:

• A. transition-property is used to specify the property that will be animated.
• B. transition-timing is used to specify the timing function for the animation.
• D. user-select is used to specify whether or not a user can select an element with the mouse or keyboard.