Conditions:
1. Some folks who live in the hills belong to the Hatfield clan; others belong to the McCoy clan.
2. No Hatfields can farm.
3. All McCoys can farm.
4. Therefore, McCoys are not Hatfields.
5. Everyone who is not a Hatfield is a horseback rider.
6. No Hatfields ride horses(from question stem)
Assume that each one of the above statements is true. Which of the following must be true if it is also true that no Hatfields ride horses.
(A) The only people who can farm are
horsebackriding McCoys. - WRONG. This is trap that fell for. 'McCoys' is fine but 'horsebackriding McCoys' is not. 'Only' is still somewhat acceptable for this choice but not without an assumption. For example - There might some other clan other than these two. If there is one then 'only' is not acceptable.
(B)
Anyone who does not belong to the McCoy clan belongs to the Hatfield clan. - WRONG. Go through point 2, 3 and 4 to understand.
(C)
All horseback riders can farm. - WRONG. Not necessarily. May be or may not be the case.
(D)
All horseback riders must be McCoys. - WRONG. From point 5 and 6.
(E) All McCoys are horseback riders. - CORRECT. A and E were the two choices between which i was moving like a pendulum. Should have understood that if D is not true then this must be true. Point 5.
Strategy-wise a point to note in these type of questions:
The options that contradict each other are probably the contenders, if not then we can get rid of the two options.
Answer E.