A、Pollution of the environment. B、Over-killing by hunters. C、A new generation of pesticide. D、Destruction of their natural homes

The bald eagle is America’s national symbol. However, the species almost went extinct 30 years ago, which lead lots of people into disappointment and depression. Nowadays, it has made a comeback.
     (23)In fact, the U. S. Fish and Wildlife Service is considering the possibility of taking it off the endangered-species list.
    Once, more than 50,000 pairs of bald eagles nested across the country. But by 1960, that number had fallen below 400. How did it happen?
    The chief killer was the widely used DDT which is a poisonous pesticide. Fish soaked up DDT, died, and were washed up on shores, where bald eagles feasted on them.
     (24)DDT prevented eagle eggshells from thickening. The shells became so thin that they shattered before the babies hatched.
    Fortunately, in 1972, a law was passed to ban the use of DDT, which saved the bald eagle from total wipeout. And since then, wildlife biologists have reintroduced bald eagles from Canada to America. The result was that last year U. S. birdwatchers counted as many as 11, 610 bald eagles in the country.
    However, even if it were dropped from the endangered list, the bald eagle would still be a "threatened species." That means the bird would continue to get the same protection — no hunting allowed, and no disturbing of nests as before.
    But bald eagles still face tough times.(25)The destruction of their natural homes could be the next DDT causing eagle numbers to drop quickly.
Questions 23 to 25 are based on the passage you have just heard.
23. What is the U. S. Fish and Wildlife Service’s consideration of bald eagles right now?
24. What harmful influence does DDT have on bald eagles?
25. According to the speaker, what may be the next DDT facing bald eagles?