GMAT Sentence Correction (SC) | Re: "[Subject 1] is SO [adj] and [Subject 2] is SO [adj] THAT" structure

78. Cherapunji receives more rainfalls than any other site of the world, yet the agriculture is so fertile and the water reservoirsare efficient, so that the water does not overflow the land; otherwise , the level of surface water would rise unexpectedly and flood most of the state’s renowned towns.
(A) are efficient, so that the water does not overflow on the land; otherwise,
(B) are so efficient that the water does not overflow the land; were it to do so,
(C) so efficient that the water does