单项选择题
A．exposing children to the new environment B．using modern facilities and equipment C．combining language lessons with games D．giving children confidence
A. half-brain sleep has something to do with icy weather B. the mystery of half-brain sleep is close to being solved C. most birds living in cold regions tend to be half sleepers D. half-brain sleep is a phenomenon that could exist among other species
A．waste B．purchase C．earn D．omit