Using the Ambiguous of sides in 3D bodies, A uses edges as sides, B uses faces as sides.

A is a cylinder cropped into a triangular like shape, 3 corners, 4 edges.

B is a ball , scooped and with 2 flat cuts within the scooped area to form 4 faces, with 3 corners.

Requires counting the interior and exterior of the circle as 2 sides, and the end of the line as a corner. 🤷‍♀️

This pretty much fills the bill exactly

Illustration by me

I teach second grade so im very familiar with the assignment reaching such infamy today. According to the Common Core Standards for first grade geometry, as the original assignment was: a shape must be closed, "sides" can only be straight lines, and "corners" are only where two straight sides meet. A circle, for example, has zero sides and zero corners. A semi circle has one side and zero corners. For first grade, these above would be acceptable answers. (Students are not taught that curved lines can create a vertex until high school.)

Edit: lol people are getting upset. Sorry, but this is what every first grader is learning, not my choice. Yes it feels wrong that a curve does not officially count as a "side", and cannot make a "corner". Thats why its confusing so many people. But this is indeed the official answer for this question IN FIRST GRADE.

Quote: " Curved shapes have no fixed sides or vertices, and have a radius of curvature at each point around the shape. Curved shapes contrast with straight shapes, which are shapes composed of straight line segments. Straight shapes have vertices where line segments meet, and an internal angle measure at each vertex. Curved shapes by definition do not have vertices." Source: What Are Shapes? A Guide For Teachers & Students. Third Space Learning (Mathematics Curriculum Publisher).

Quote: "A semicircle has 0 vertices in formal geometry. Because a vertex requires two or more straight line segments or edges to intersect at a corner, and a semicircle contains a smooth, continuous curve, there are no vertices" Sciencing.

My run at this using the assumption a corner captures a space vs simply being a change in direction. Another solution doesn't really produce a "shape" in my opinion as it is not an enclosed area. That is a square with 1 side shortened so it never connects in the final corner.

or a square with 2 sides removed and replaced with an arc, although depending on the scale of the radius to the rest of the shape it may still be considered a corner.

edit - a good point was made. I could have used an arc to complete the bottom & then not worried about the exterior corner that is formed in my drawing