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 E1 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.

单选题 Which of the following is NOT a possible reason for whales dying?
A. Pneumonia. B. Brain infection. C. Over-population. D. Over-eating.

单选题 Why might the increasing number of whales cause problems with their health?
A. There's not enough room for them in Alaska.
B. There may not be enough food for them in Alaska.
C. They get pushed ashore.
D. There are more whales to spread disease.

单选题 One reason it is difficult to know why the whales are dying is that ______.
A. the whales travel such a long distance
B. there are more whales than there used to be
C. the whale bodies are too old to study by the time they are found
D. the whales are endangered

单选题 About how many more whales have been sighted in the San Francisco Bay this year compared to last year?
A. Twice as many.
B. Three times as many.
C. Half as many.
D. About the same.