IMO E
(A) The government is unlikely to approve the synthetic hormone BST for use in cows---> govt approval is not dependent on health of cows
(B) The proportion of cows that suffer from udder inflammation decreased fertility, and symptoms of stress are currently greater on big dairy farms than on small ones.---Passage mentions only the overall cost, it does not mean large farm owners have greater cost per cow than small owners
(C) At the present time, milk from cows raised on small farms is safer to drink than milk from cows raised on big farms.--No metion of quality is given
(D) The milk from cows who receive BST will not be safe for people to drink.---No mention of quality
(E) Owners of big farms stand to gain more from government approval of BST than do owners of small farms. --> Owners of big farm gain more than small farm per cow, bcz it means that milk will be increased and hence more money but with less medical care cost per cow,; whereas small farm milk will increase with high medical care cost, therefore large farm will gain more than small farm