Federal agricultural programs aimed at benefiting one group whose livelihood depends on farming often end up harming another such group.

Which of the following statements provides support for the claim above?

I. An effort to help feed-grain producers resulted in higher prices for their crops, but the higher prices decreased the profits of livestock producers.

II. In order to reduce crop surpluses and increase prices, growers of certain crops were paid to leave a portion of their land idle, but the reduction was not achieved because improvements in fficiency resulted in higher production on the land in use.

III. Many farm workers were put out of work when a program meant to raise the price of grain provided grain growers with an incentive to reduce production by giving them surplus grain from government reserves.

(A) I, but not Ⅱ and not III

(B) Ⅱ, but not I and not III

(C) I and III, but not Ⅱ

(D) Ⅱ and III, but not I

(E) I,Ⅱand III

I is a must. II can be ruled out. Why III ? I don't understand what it means.

Thanks!

III：很多farm workers 因此而失业了，所以也符合benefiting one group while harming another group.

还是请教关于III，政府的目的是raise the price of grain，并没有明确是要帮助哪一个group啊？

为什么要选呢？