C)

Not sure if many of is the right idiom... Many a sounds more correct

IMO B
A) becomes the dominant languaje of the Mexicans, having replaced many local languajes ( Becomes- present tense. we need a past tense)- wrong.

B) became the dominant languaje of the Mexicans, replacing many of the local languajes (modifies correctly. correct tense- past tense.)- correct

C) became the dominant languaje of the Mexicans, replacing many a local languaje('many a local language' is wrong. a local language implies singular. how can you have 'many' in a singular object?)- wrong.

D)becomes the dominant languaje of the Mexicans, and it replaced many of the local languajes (same tense error as in A. past tense is required)

E)becomes the dominant languajeof the Mexicans, replacing many a local languaje ( past tense required)

I agree with fibbonnaci, how ever the OA is: B

Any comment??