GMAT Sentence Correction (SC) | Between 14,000 and 8,000 b.c. the ice cap that covered northern Asia,

Between 14,000 and 8,000 b.c. the ice cap that covered northern Asia, Europe, and Americabegan to melt, uncovering vast new areas that were to be occupied by migrating peoples moving northward.

A.began to melt, uncovering vast new areas that were to beoccupied
Correct
B.began melting, to uncover vast new areas to be occupied
-- Changes the original intent of the sentence, conveying ICE CAPS began uncovering vast areas DIRECTLY. Original intent is "Vast areas were uncovered as a result of Melting