GMAT Sentence Correction (SC) | Re: Unlike the Gregorian calendar, the synchronization of the

Unlike the Gregorian calendar, the synchronization of the calendar year with the astronomical year in the Chinese calendar is not achieved by intercalating a day once every four years, but by adding an intercalary month about once every three years.

(A) -
(B) The Gregorian calendar, unlike the Chinese calendar, achieves the synchronization of the calendar year with the astronomical year by intercalating
(C) Unlike the Gregorian calendar, the astronomical year is synchronized with the calender