In Microsoft PowerPoint the entry effect as one slide replaces another in a show is called a (an)

Answer: Option B

In Microsoft PowerPoint, the entry effect as one slide replaces another in a show is called a (an) Option B: slide transition. Slide transitions define how one slide is replaced by the next during a presentation, adding visual effects such as fades, wipes, or zooms.
Option A: animation refers to effects applied to individual elements (like text or images) within a slide.
Option C: custom animation allows you to apply specific animations to different elements on a slide.
Option D: preset animation typically refers to predefined animations that you can apply to elements on a slide.
Therefore, the correct answer in this context is Option B: slide transition.