根据以下材料，回答题
To live in the United States today is togain an appreciation for Dahrendorf′s assertion that social change existseverywhere. Technology, the application of knowledge for practical ends, is a majorsource of social change.
Yet we would do well to remind ourselvesthat technology is a human creation; it does not exist naturally. A spear or arobot is as much a cultural as a physical object. Until humans use a spear to huntgame or a robot to produce machine parts, neither is much more than a solid massof matter. For a bird looking for an object on which to rest, a spear or robotserves the purpose equally well. The explosion of the Challenger space shuttleand the Russian nuclear accident at Chemobyl drive home the human quality oftechnology; they provide cases in which well-planned systems suddenly wenthaywire and there was no ready hand to set them right. Since technology is ahuman creation, we are responsible for what is done with it. Pessimists worrythat we will use our technology eventually to blow our world and ourselves topieces. But they have been saying this for decades, and so far we have managedto survive and even flourish. Whether we will continue to do so in the yearsahead remains uncertain. Clearly, the impact of technology on our livesdeserves a closer examination.
Few technological developments have had agreater impact on our lives than the computer revolution. Scientists andengineers have designed specialized machines that can do the tasks that onceonly people could do. There are those who assert that the switch to aninformation-based economy is in the same camp as other great historicalmilestones, particularly the Industrial Revolution. Yet when we ask why theIndustrial Revolution was a revolution, we find that it was not the machines.The primary reason why it was revolutionary is that it led to great socialchange. It gave rise to mass production and, through mass production, to asociety in which wealth was not confined to the few.
In somewhat similar fashion, computers promiseto revolutionize the structure of American life, particularly as they free thehuman mind and open new possibilities in knowledge and communication. TheIndustrial Revolution supplemented and replaced the muscles of humans and animalsby mechanical methods. The computer extends this development to supplement andreplace some aspects of the mind of human beings by electronic methods. Andit′s the capacity of the computer for solving problems and making decisionsthat represents its greatest potential and that poses the greatest difficultiesin predicting the impact on society.

Why does the author mention theexplosion of the Challenger space shuttle and the Russian nuclear accident atChemoby1 查看材料

A.To show the worry that technology mayeventually destroy our world.
B.To tell the readers that as a humancreation, technology may go wrong and do harm to human.
C.To emphasize the responsibility we havein ensuring human safety in a technological world.
D.To stress the fact that technologyusually goes wrong if not given close examination.