Answer:
The first option. "If lines on a coordinate plane have opposite reciprocal slopes, then they are perpendicular."
Explanation:
It is the only one that makes sense, tbh. But, it includes the proper "if-then" form like the question requests it have. It also incorporates all aspects of the original statement-
a.) lines on a coordinate plane
b.) perpendicular
c.) opposite reciprocal slopes.
You're welcome. :D