To solve this question, let's analyze the properties of the diagonals of a square.
1. Understanding the Shape:
- A square is a quadrilateral with all four sides of equal length.
- All internal angles in a square are 90 degrees.
2. Properties of the Diagonals of a Square:
- In a square, there are two diagonals.
- These diagonals are equal in length.
- Each diagonal bisects the square into two congruent right-angled triangles.
- The diagonals of a square intersect each other at right angles (90 degrees).
3. Analyzing the Options:
- Option A (parallel): This is incorrect because in a square, the diagonals actually intersect each other and are not parallel.
- Option B (sometimes equal): This is incorrect because in a square, the diagonals are always equal, not just sometimes.
- Option C (perpendicular): This is correct because the diagonals of a square always intersect each other at a right angle (90 degrees), making them perpendicular.
- Option D (never congruent): This is incorrect because the diagonals of a square are always congruent, meaning they have the same length.
Based on the analysis, the correct answer is:
C. perpendicular
