The correct choice is A. There is an example as follows:
It is a tough business for the farmer who does most of the work, faces rising production costs but gets a relatively small piece of the financial return.
In other way, the above sentence could be altered as:
For the farmer who does most of the work, facing rising production costs but getting a relatively small piece of the financial reture, it is a tought business.
E creates illogical confusion that the farmer is "provided with high-energy feed, and milked regularly". Farmer 定时被挤奶,呵呵,有趣!
A uses -ing to illustrate how the farmer keep the them (cows) cool - providing them..., milking them.... The plural nuns "them" will not create confusion with singular "farmer", and agrees with plural subjects "Holstein cows".