Final answer:
The altitude of a triangle is always perpendicular to a side of the triangle as it forms a 90° angle with the side. The other options, median, angle bisector, and perpendicular bisector, do not always have this perpendicular relationship. The correct answer is b) Altitude.
Step-by-step explanation:
The answer to the question 'Which of the following are always perpendicular to a side of a triangle?' is b) Altitude. An altitude of a triangle is a segment from a vertex of the triangle to the line containing the opposite side and is perpendicular to that side.
This means the altitude forms a 90° angle with the side of the triangle. The other options such as median, angle bisector, and perpendicular bisector do not always meet this condition.
A median connects a vertex to the midpoint of the opposite side but is not necessarily perpendicular. An angle bisector divides the angle at a vertex into two equal angles, also not necessarily creating a perpendicular line.
Finally, a perpendicular bisector is a line that is perpendicular to a side of a triangle at its midpoint; while it is perpendicular, it is not drawn from a vertex and thus is not always considered to be perpendicular to a specific side in terms of originating from a vertex like an altitude does.