单项选择题
A．half-brain sleep is found in all kinds of birds B．half-brain sleep is characterized by accelerated brain waves C．birds can control their half-brain sleep consciously D．birds always sleep with the whole of their brain at rest
A．To make a comparison between the past and the present. B．To honor her father. C．To criticize the past. D．To criticize the present.
A．capable of using two languages B．both clever and confident C．aware of their own limitations and strengths D．independent of their parents