Bigger-brained birds survive better than their feathered friends with smaller brains, according to a study published on Tuesday. Scientists have suspected that birds with large brains in relation to their body size lived longer because they were able to adapt their behavior to environmental challenges. Now they have provided evidence that it does. "We have tested the hypothesis  that the brain can buffer  animals against the environment and help them to survive when they face environmental challenges," said Daniel Sol of the Centre for Ecological Research and Forestry Applications in Barcelona, Spain. After comparing death rates, brain size and body mass of 236 species of birds from different regions of the world, Sol and scientists in Britain, Hungary and Canada discovered that the bigger the brain the better. Crows and parrots have the largest brains, while pheasants   have a relatively small brain. Earlier studies have shown there is a relationship between the size of the brain and an animal's capacity to create new behavior and adapt more easily. "The idea is that if you have a big brain, you are more capable of adjusting behavior and responding to environmental changes. This can help you to survive," said Sol, who reported the finding in the journal Proceedings of the Royal Society B: Biological Sciences. Tamas Szekely of the University of Bath in England and a co-author of the report, said birds were ideal to test the hypothesis because they are the only species in which brain size and behavioral response to environmental challenges such as climate and habitat destruction is understood. The finding of bird's brains recently refers to   _  .
the smaller brain the birds have, the longer they live the smaller brain the birds have, the cleverer they are the bigger brain the birds have, the larger their bodies are the bigger brain the birds have, the abler they are to deal with environment
Question: Bigger-brained birds survive better than their feathered friends with smaller brains, according to a study published on Tuesday. Scientists have suspected that birds with large brains in relation to their body size lived longer because they were able to adapt their behavior to environmental challenges. Now they have provided evidence that it does. "We have tested the hypothesis  that the brain can buffer  animals against the environment and help them to survive when they face environmental challenges," said Daniel Sol of the Centre for Ecological Research and Forestry Applications in Barcelona, Spain. After comparing death rates, brain size and body mass of 236 species of birds from different regions of the world, Sol and scientists in Britain, Hungary and Canada discovered that the bigger the brain the better. Crows and parrots have the largest brains, while pheasants   have a relatively small brain. Earlier studies have shown there is a relationship between the size of the brain and an animal's capacity to create new behavior and adapt more easily. "The idea is that if you have a big brain, you are more capable of adjusting behavior and responding to environmental changes. This can help you to survive," said Sol, who reported the finding in the journal Proceedings of the Royal Society B: Biological Sciences. Tamas Szekely of the University of Bath in England and a co-author of the report, said birds were ideal to test the hypothesis because they are the only species in which brain size and behavioral response to environmental challenges such as climate and habitat destruction is understood. The finding of bird's brains recently refers to   _  .
A. the smaller brain the birds have, the longer they live
B. the smaller brain the birds have, the cleverer they are
C. the bigger brain the birds have, the larger their bodies are
D. the bigger brain the birds have, the abler they are to deal with environment
Answer: