It is certain that at least as many migratory birds fly through Hilden

Official Explanation

(A) No. We are not given any information as to how average snowfall might impact migratory bird flight patterns.

(B) No. We don’t know whether migratory birds are susceptible to the disease or if they might in fact be carriers of the disease. If they are carriers of the disease, then the fact that the disease has been diagnosed in Paluska would not necessarily affect the levels of migratory birds flying through either Hilden or Paluska.

(C) Yes. If Paluska is a town in Hilden County, then birds that fly through Paluska are also flying through Hilden County. So at least as many birds fly through Hilden as fly through Paluska. The following diagram might be helpful in conceptualizing this problem.

(D) No. Knowing that more natural predators have been reported in Hilden does not verify that there actually are more predators in Hilden. Furthermore, we don’t know the sizes of Hilden and Paluska. If Paluska is very small and Hilden is very large, the fact that more predators have been sighted in Hilden would not be significant to this passage.

(E) No. Again, while population density might impact migratory bird patterns, we don’t know how big Paluska and Hilden are. If Hilden’s area exceeds Paluska’s area significantly, the fact that Hilden has a bigger population might not affect the numbers of migratory birds that fly through each place.