Prove that two reflections, s and t, commute, if and only if their mirrors are perpendicular to each other. Which of the following options correctly represents the condition for the commutation of two reflections?

A) s and t commute if their mirrors are parallel to each other.
B) s and t commute if their mirrors are perpendicular to each other.
C) s and t commute if their mirrors are at a 45-degree angle to each other.
D) s and t commute if their mirrors are at a 90-degree angle to each other.