Which of the following CSS properties is necessary for an animation to be smooth when hover is activated?

The property that is necessary for an animation to be smooth when hover is activated is transition. This CSS property allows you to define the timing and the duration of the change that occurs when a CSS property is altered, such as on hover. By specifying a transition, you can create gradual changes between the original state and the hovered state, resulting in a smoother and more visually appealing effect.

Without the transition property, any change that occurs when hovering over an element would happen instantly, instead of smoothly animating over a set period of time. This abrupt change can often feel jarring to users. In contrast, when you use transition, you can control aspects like duration, easing functions, and which properties should transition smoothly. Therefore, including the transition property is essential for creating fluid and engaging hover effects in web design.