下图为1950～2010年世界及亚洲、欧洲、非洲、北美洲人口变化过程。根据相关知识，读下图完成下列各题。

    The best way to deal with sports injuries is to keep them from happening in the first place. Knowing the rules of the game you're playing and using the right ____(equip) can go a long way toward preventing injuries. If you think you've been injured, pull ____(you) out the game or stop ____(do) your activity or workout. Let a coach or parent know what happened in case you need to see a doctor. Serious head and neck injuries happen most often in athletes ____ play body-contact sports like football. Keep the injured person still with his or her head ____ (hold) straight while someone calls for emergency ____(medicine) help. If the person ____(lie) on the ground, do not try to move him or her.

    Your first question after a sport injury will ____(probable) be, “When can I play again?” This depends on the injury and what your doctor tells you. Even if you can't return to your sport right away, a doctor might have suggestions and advice ____ what you can do to stay fit. Always check with your doctor ____ trying any activity following an injury.

反比例函数y= $\frac{k}{x}$ 的图像过点P（2，6），那么k的值是____