Choose the word which is different from the rest.

Circle
Ellipse
Sphere
Cube

The answer is D. Cube.

A circle is a round shape with no corners. An ellipse is a shape that is round in one direction and flat in the other. A sphere is a round shape with no flat sides. A cube is a shape with six flat sides that are all the same size.

The cube is the only shape that is not round.