Which command key is designated for reducing the size of the timeline?

The command key designated for reducing the size of the timeline is associated with the function of playback control. In many video editing software applications, the K key is commonly used to pause or play the timeline. However, in this specific context, the correct answer for reducing the size of the timeline aligns with the correct function as it relates to navigating and controlling the timeline's view by allowing the user to adjust how much of the timeline is visible at once.

This ability to zoom in or out on the timeline is essential for editors to focus on specific parts of a project or to get an overview of the entire timeline, which is a key part of efficient video editing. The other command keys do not serve the same purpose and are often linked to different functions within the editing software, such as playing forward or backward without the ability to adjust the timeline’s visual scope.