Explanation:

A diagonal is a line segment that connects two nonadjacent vertices of a polygon. In the case of a triangle, a diagonal would connect two vertices that are not adjacent to each other.

A triangle has three sides and three vertices. Let's label the vertices as A, B, and C.

To count the number of diagonals, we need to connect each vertex to every other vertex that is not adjacent to it.

Connecting vertex A:
- A cannot be connected to itself, so we eliminate one possibility.
- A can be connected to B, which forms one diagonal.
- A can be connected to C, which forms another diagonal.

Connecting vertex B:
- B cannot be connected to itself, so we eliminate one possibility.
- B can be connected to A, which forms one diagonal.
- B can be connected to C, which forms another diagonal.

Connecting vertex C:
- C cannot be connected to itself, so we eliminate one possibility.
- C can be connected to A, which forms one diagonal.
- C can be connected to B, which forms another diagonal.

Total number of diagonals:
Adding up all the possibilities, we have a total of 2 + 2 + 2 = 6 diagonals.

However, we need to remember that a diagonal must connect two nonadjacent vertices. In a triangle, all the vertices are adjacent to each other. Therefore, no diagonals can be formed within a triangle.

Hence, the correct answer is option C: 0 diagonals.