The Maya built cities and ceremonial centers that for reasons still unknown they abandoned in the tenth century, and left the jungle to cover them.
(A) The Maya built cities and ceremonial centers that for reasons still unknown they abandoned in the tenth century, and left
(The Maya built cities and ceremonial centers...and left the jungle. They didn't leave the jungle in fact they left it to the jungle to cover the cities etc. Illogical meaning. Incorrect)(B) For reasons still unknown, in the tenth century the Maya abandoned the cities and ceremonial centers they had built, leaving
(The only contention here could be use of they, therefore quoting Manhattan SC Guide "The words majority, minority, and plurality are either singular or plural, depending on their context. If you want to indicate the many individual parts of the totality, use a plural verb. If you want to indicate the totality itself, then use a singular verb form". Here The Maya indicates people and people will always be plural as mentioned correctly by AjiteshArun. Also leaving is correctly used to express that they left it to the jungle to cover the cities etc. Best choice) (C) Still unknown are the reasons for which the Maya abandoned in the tenth century the cities and ceremonial centers they had built, and left
(Same error as in option A)(D) In the tenth century and for reasons still unknown, the Maya had abandoned the cities and ceremonial centers they built, and left
(Same error as in option A)(E) The cities and ceremonial centers the Maya built were abandoned for reasons still unknown in the tenth century, leaving
(abandoned for reasons still unknown in the tenth century...incorrectly means that reasons were unknown in the tenth century).Although IMO, there are a lot more errors in wrong answer choices, I have only mentioned those which I could quickly spot to eliminate the incorrect choices.