Odd One Out: Cylinder

Explanation:
A) Triangle: A triangle is a polygon with three sides and three angles. It is a two-dimensional shape.
B) Square: A square is a polygon with four equal sides and four right angles. It is also a two-dimensional shape.
C) Cylinder: A cylinder is a three-dimensional shape with two circular bases and a curved surface connecting the bases.
D) Circle: A circle is a two-dimensional shape with a curved boundary and all points on the boundary are equidistant from the center point.

The odd one out in this group is the cylinder. Here's why:

1. Different Dimensions:
- The triangle, square, and circle are all two-dimensional shapes, meaning they exist in a plane and have length and width.
- The cylinder, on the other hand, is a three-dimensional shape as it has height along with the length and width.

2. Different Structures:
- The triangle and square have straight sides and angles, while the circle has a curved boundary.
- The cylinder has a curved surface connecting two circular bases.

3. Different Properties:
- The triangle and square are polygons, which are closed shapes formed by straight lines.
- The circle is not a polygon as its boundary is a curved line.
- The cylinder is not a polygon either as it has curved parts.

4. Different Uses:
- Triangles and squares are commonly used in various fields such as architecture, engineering, and design.
- Circles are often used to represent wheels, planets, and other round objects.
- Cylinders are commonly seen in everyday objects like cans, bottles, and tubes.

In conclusion, the odd one out among the given options is the cylinder because it is the only three-dimensional shape in the group, while the others are two-dimensional shapes.

Rest all are 2-D shapes.