A、Plants. B、Sun. C、Animals. D、Human beings. B本题要适应听力题，由对话到文章的转变，尤其是要听懂第一句“All food chains begin with the sun.”如果第一句漏掉了，可以根据后面的文章

All food chains begin with the sun, and all food chains become broken up if one of the links disappears.
   All life depends on energy from sunlight. Only plants can use this energy directly. Their leaves are little factories that use sunlight to make food from water and things in the soil and air.
   Plants in turn feed all other living things. Animals can only use the sun’s energy after. it has been changed into food by plants. Some animals feed directly on plants, others eat smaller animals. Meat-eating animals are only eating plants indirectly.     What about human beings? We are members of many food chains. We eat vegetables and fruit. We also eat meat and drink milk. This means the sun’s energy passes through plant to animal before it reaches us.
   Nature is a great thing. Any food chain always produces enough for each of its members if it is left alone. When there isn’t enough food for any link in the chain, some of its members die off. So the balance is always kept.
According to this article, what are all food chains connected with?