Answer IMO C
"Unlike or contrasting words" should be followed by "NOUN X", "NOUN Y"
-> Only C does that correctly. Other options are comparing "terms" with "Presidents" that does not make sense logically.
Bunuel wrote:
Unlike the terms served by Grover Cleveland, separated by four years, all former two-term U.S. Presidents have served consecutive terms.
(A) Unlike the terms served by Grover Cleveland, separated by four years
(B) Besides the terms of Grover Cleveland that were separated by four years
(C) Except for Grover Cleveland, whose terms were separated by four years
(D) Aside from the terms of Grover Cleveland that were separated by four years
(E) Other than the separated terms of Grover Cleveland, of four years