下列哪一组动物都是恒温动物( )
A:眼镜蛇和狮子
B:喜鹊和斑马
C:海龟和虎
D:壁虎和猩猩
My grandfather began to use the computer in his ____(六十多岁).
已知直线AB与CD是异面直线,求证:直线AC与BD也是异面直线.