DeeptiM wrote:
C talks about Tattersall warblers...which is not even mentioned in the passage...
pls help understand how did you choose C
A term, noun or a premise can be introduced from outside in case of weaken and strengthen type questions. C strengthens the author's conclusion that Croton's jays lack navigational skill to travel south by showing that they don't need crookbeaks for anything else except for the navigation. The hint is provided by showing that Croton's jays follow another species altogether to travel north because they also take them to their destination. The only concern I had was the word "north"; the argument talks about south. However, if we just generalize the conclusion by saying that the jays lack migrating navigation skill altogether, C fits in.
"A" weakens the argument by showing an alternate reason for tailgating. It says; no-no, jays follow crookbeaks because they need a place to usher their eggs, not because they need navigation.
"B" talks about a completely out of scope fact. Croton jays are not even mentioned.
"D" doesn't say anything about Croton's jays. We need to know whether jays need navigation and here's "D", talking about other species that don't concern the problem in hand.
"E" says crookbeaks migrate north in spring. Conclusion is about the lacking navigational skill to travel South. At best, it actually weakens the argument by suggesting that jays will travel north without crookbeaks help. But, who knows if they have some other buddies who can help them get to north; someone like Tattersall warblers. However, we shouldn't assume that.
Ans: "C"