A、Body size. B、Migration route. C、Food preference. D、Population growth. D最后一句话讲到，这种变化会很大程度。impact a species’population growth，因此

What’s good for adults is not always best for the young, and vice versa. At least that is the case with some sparrows and how they experience the effects of climate change, according to two recent studies by scientists at the University of California, Davis and Point Blue Conservation Science.
    Both studies show the importance of considering the various stages and ages of individuals in a species from babies to juveniles to adults to best predict not only how climate change could affect a species as a whole, but also why. In the study, published in print today in the journal Global Change Biology, Climate Change had opposite projected effects for adult and juvenile song sparrows in central coastal California.
    The researchers found not surprisingly, that adult survival was sensitive to cold winter weather. Even though we rarely see freezing temperatures on the coast of California, it was clear that the adult birds chances of survival were lowest in the coldest winter. They expected a similar response from the young, however, warmer, dryer winter is translated to less food for the juvenile sparrows during the following summer. Before they can get to winter, the juveniles have to survive their first summer when they’re sensitive to how much food is available. So as winter gets warm, we expect adults and juveniles to respond in opposite directions.
    In another recent study of song sparrows published in the journal Ecology, researchers found that parents provided a buffer against the weather for baby sparrows still dependent on them or food. However, independent juveniles that were newly out on their own were more sensitive to changes in the weather because they lacked the skills and experience of their parents. While that vulnerability has existed for as long as offspring have been leaving the nest, climate change is expected to worsen those already uncertain conditions. This sort of variation in juvenile survival can significantly impact a species’ population growth.
    Questions 26-30 are based on the passage you have just heard:
    26. What is the main idea of this talk?
    27. When is the lowest chances of survival for the adult song sparrows?
    28. Why does a warmer winter make it difficult for the juvenile song sparrows to survive the following summer?
    29. What can we learn about the baby song sparrows?
    30. In what aspects does climate change affect the species the speaker is talking about?