尼克父亲教导过他的一句话，他至今念念不忘（）
参考答案：对
My sister had beautiful black long _____ but I could see some white _____.
A．hairs, hair
B．hair, hairs
C．hairs, hairs
D．hair, hair
已知△ABC的重心G到BC边上中点D的距离为2，那么中线AD长为______．
