Which term describes a motion tween that can be reused after customization?

The correct term that describes a motion tween that can be reused after customization is "Preset." In Adobe Animate, presets are pre-configured animations or tweens that can be applied to different objects within your project. This means that once you customize a motion tween to fit a specific need, you can save it as a preset, allowing for efficient reuse in other parts of your animation or in future projects.

Using presets can significantly streamline the animation process, as you don’t need to recreate the same motion tween from scratch every time it’s needed. Instead, you can apply the preset to different objects, making adjustments as necessary, which saves time and enhances workflow efficiency.

The other terms present don't carry the same meaning in the context of creating reusable animations. Instances refer to copies of symbols that appear in the animation; a mask is used for concealing parts of an image, creating interesting visual effects; while symbols represent reusable graphic objects but don’t specifically relate to motion tweens in terms of customization and reuse.