I WILL GIVE BRAINLIEST!!!

Last summer Jim mowed just one lawn, now he mows three.

Which identifies the sentence in which the revisions are not grammatically correct?

A. Last summer Jim mowed just one lawn, but now he mows three.

B. Last summer Jim mowed just one lawn. Now he mows three.

C. Last summer Jim mowed just one lawn; now he mows three.

D. Last summer Jim mowed just one lawn now he mows three.