Answer:
2). Because many executives have access to company jets, boards of directors have a responsibility to ensure that shareholders are not footing the bill for personal travel.
Step-by-step explanation:
As per the question, option 2 i.e. 'Because many executives have access to company jets, boards of directors have a responsibility to ensure that shareholders are not footing the bill for personal travel' displays the most appropriate revision of the given sentence as it correctly employs comma in it. Since the dependent clause('Because many executives have access to company jets') precedes the independent clause in the given complex sentence, the use of a comma(,) after the subordinate(dependent clause) is grammatically correct. The other options fail to consider this point as they either don't employ a comma(option 1) or use it incorrectly(options 3 and 4). Thus, option 2 is the correct answer.