Correct Answer: (d) The old woman
Note: Use "who commute long distances" in place of "who commuting long distances". Who is the relative pronoun here. The antecedent for who is "jobs". According to the pronoun rule the verb used after the relative pronoun(who) will be according to the antecedent (jobs) so the verb will be plural and "commute" will be used. So, "People with full time sedentary jobs who commute long distances, may have sleep problems due to lack of exercise" is the correct sentence.