单选题 Every year gray whales migrate from the Bering Sea in Alaska to the Baja Peninsula in Mexico.
Eleven gray whales have died in the San Francisco Bay in the last three weeks. No one knows why the whales are dying.
Last year 270 whales died along the whales' migration route. Many people think starvation is the cause. This year the dead whales seem to have more blubber (fat) on them.
Twenty years ago, the gray whale was listed as an endangered species.
Some scientists think that the larger number of whales makes it hard to find enough food. More whales create more pressure on the food supply, a supply that some scientists say may have dwindled as a result of the warm waters of El Nino.
Most of the whales have been dead for many days before they are found and studied. This makes it hard to find the reason for death.
65 whales have been seen in the San Francisco Bay Area this year compared to 17 last year. The whales could be dying from many diseases, but it may be over-population.

【正确答案】 D

【答案解析】参见第五段。作者特别提到由于鲸鱼的数量巨大，因此它们很可能没有足够的食物。因此，过量饮食是不可能的。由于人们还没有真正弄清楚鲸鱼的死因，那么，任何其他的原因都是可能的。