Geometry

Question Analysis
This question involves deriving the contrapositive of a statement about perpendicular lines.

Key Concept Explanation:
The contrapositive of "If P, then Q" is "If not Q, then not P."

Step-by-Step Solution:
Original statement: "If two lines are perpendicular (P), then they intersect at a 90-degree angle (Q)."
Contrapositive: "If two lines do not intersect at a 90-degree angle (not Q), then they are not perpendicular (not P)."
The correct answer is B.

Option Analysis:
A: This is the converse, not the contrapositive.
B: Correct contrapositive.
C: This is the inverse, not the contrapositive.