Choice "C" is correct. C corporations may adopt any year end, provided the year end is approved by the IRS.
Choice "b" is incorrect. S corporations must generally adopt a calendar year end; however, certain S corporations may establish a valid business purpose for a different fiscal year by filing an election using Form 8716.
Choice "d" is incorrect. Limited liability companies generally elect to be taxed as partnerships. Partnerships must generally use the year end of the majority of its partners. If there is no majority, then the partnership must generally use a calendar year end.
Choice "a" is incorrect. All trusts (except tax-exempt trusts) must use a calendar year end.