单项选择题
A．jump as high as you can B．slide down a rope to the ground C．attach yourself to a rope and fall to the ground D．fall towards the ground without a rope
A．they have a lot of free time B．they can go to hospital if they are injured C．their lives lack excitement D．they no longer need to hunt for food
A．Human beings B．animals C．plants and animals D．man and wild animals