What's the meaning of the word "elastic" (Line 2, Para 2)（）

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．are trying activities such as bungee jumping
B．are climbing the highest mountains
C．are close to death in sports
D．are looking for adventures such as exploring unknown places