Answer:
The correct answer is "Hiking tours are arranged by the Sierra Club, P.O. Box 7959, San Francisco, CA 94120."
Explanation:
The proper way to write a location is to separate each element of the location by using a comma (,), avoiding any possible confusion. The third option is the one that is properly written, using a comma to separate "the Sierra Club" and "P.O. Box 7959" and other comma to separate "San Francisco" and "CA".
