Managing your irrigation system well and watering your grass wisely not only saves water, but helps to ensure the success of your lawn.

A. saves water, but helps to ensure the success of your lawn
B. saves water, but also help to ensure the success of your lawn
C. saves water, but the success of your lawn is more helpfully ensured
D. save water, but also help to ensure the success of your lawn
E. save water, but also the success of your lawn is more helpfully ensured

OAD
Source: GmatClub

Can some one explain me what is wrong with A?