gwd 6-30

Q30:

Each year red-winged blackbirds stop in a certain region of Midland
                    Province on their spring and fall migrations.  In the fall, they eat a significant portion of the province’s sunflower crop.  This year Midland farmers sought permits to set out small amounts of poisoned rice during the blackbirds’ spring stop in order to reduce the fall blackbird population.  Some residents voiced concern that the rice could threaten certain species of rare migratory birds.  Nevertheless, the wildlife agency approved the permits.

Which of the following, if true, most helps to justify the wildlife agency’s approval of the permits, given the concerns voiced by some residents?

1. In the region where the red-winged blackbirds stop, they are the first birds to be present in the spring.
2. The poison that farmers want to use does not kill birds but rather makes them incapable of producing viable eggs.
3. Since rice is not raised in Midland
                           Province, few species of birds native to the province normally eat rice.
4. Without the permit, any farmers shown to have set out poison for the blackbirds would be heavily fined.
5. The poison that farmers got approval to use has no taste or smell that would make it detectable by birds.

ans is a,why c is incorrect?

文章说对“稀有的迁徙鸟有威胁”

C说本土的鸟都不吃。C就没有什么意义了