单选题 Around the world more and more people are taking part in dangerous sports and activities.Of course，there have always been people who have looked for adventure--those who have climbed the highest mountains，explored（探险）unknown parts of the world or sailed in small boats across the greatest oceans.Now，however，there are people who seek（寻找）an immediate thrill（令人激动的事情）from a risky activity which may only last a few minutes or even seconds．

I would consider bungee（蹦极）jumping to be a good example of such an aetwity.You jump from a high place（perhaps a bridge or a hot air balloon）200 metres above the ground with an elas-tic（弹性的）rope tied to your ankles.You fall at up to 150 kilometres an hour until the rope stops you from hitting the ground.It is estimated that 2 million people around the world have now tried bungee jumping.Other activities which most people would say are as risky as bungee jumping involve（包括）jumping from tall buildings and diving into the sea from the top of high cliffs．Why do people take part in such activities as these Some psychologists（心理学家）suggestthat it is because life in modern societies has become safe and borin9.Not very long ago，people’s lives were constantly under threat.They had to go out and hunt for food，diseases could not easily be cured，and life was a continuous battle for survival.

Nowadays，according to many people，life offers little excitement.They live and work in comparatively safe environments;they buy food in shops;and there are doctors and hospitals to look after them if they become ill.The answer for some of these people is to seek danger in activities such as bungee jumping.

People probably take part in dangerous sports nowadays because__________.