GRE Reading Comprehension: ETS-GRE阅读ETS - 3211DD22C9130DIK7

According to the passage, which one of the following factors may help account for the occurrence of neurogenesis in canaries? A. the life span of the average canary B. the process by which canaries learn songs C. the frequency of canary breeding seasons D. the number of regions in the canary brain related to song learning E. the amount of time an average canary needs to learn a repertoire of songs