Which option can be used to refine the speed and duration of an animation within After Effects?

Keyframe Interpolation is essential for refining the speed and duration of animations in Adobe After Effects. This method utilizes keyframes, which are markers that define specific values at certain points in time. By adjusting the interpolation method between keyframes, users can control how the animation dynamically accelerates or decelerates.

For example, utilizing linear interpolation results in a consistent speed between keyframes, while ease-in and ease-out options can create smooth transitions that start or end slowly before accelerating. This level of control allows for a more nuanced and professional-looking animation.

Other options like Time Stretch can alter the overall duration of a layer, but it does not provide the same granular control over how the animation progresses between specific points. Animation Rate Setting isn't a standard term used within After Effects, and Frame Blending is focused on smoothing motion between frames rather than controlling keyframe timing. Therefore, Keyframe Interpolation is the most suitable and effective choice for refining speed and duration in animations.