单选题：根据材料请回答下列题目：Into the UnknownThe world has never seen populat

根据材料请回答下列题目：
Into the Unknown
The world has never seen population ageing before. Can it cope?
Until the early 1990s nobody much thought about whole populations getting older. The UN had the foresight to convene a “world assembly on ageing” back in 1982, but that came and went. By 1994 the World Bank had noticed that something big was happening. In a report entitled “Averting the Old Age Crisis”, it argued that pension arrangements in most countries were unsustainable.
For the next ten years a succession of books, mainly by Americans, sounded the alarm. They had titles like Young vs Old, Gray Dawn and The Coming Generational Storm, and their message was blunt: health-care systems were heading for the rocks, pensioners were taking young people to the cleaners, and soon there would be intergenerational warfare.
Since then the debate has become less emotional, not least because a lot more is known about the subject. Books, conferences and research papers have multiplied. International organisations such as the OECD and the EU issue regular reports. Population ageing is on every agenda, from G8 economic conferences to NATO summits. The World Economic Forum plans to consider the future of pensions and health care at its prestigious Davos conference early next year. The media, including this newspaper, are giving the subject extensive coverage.
Whether all that attention has translated into sufficient action is another question. Governments in rich countries now accept that their pension and health-care promises will soon become unaffordable, and many of them have embarked on reforms, but so far only timidly. That is not surprising: politicians with an eye on the next election will hardly rush to introduce unpopular measures that may not bear fruit for years, perhaps decades.
The outline of the changes needed is clear. To avoid fiscal (财政) meltdown, public pensions and health-care provision will have to be reined back severely and taxes may have to go up. By far the most effective method to restrain pension spending is to give people the opportunity to work longer, because it increases tax revenues and reduces spending on pensions at the same time. It may even keep them alive longer. John Rother, the AARP’s head of policy and strategy, points to studies showing that other things being equal, people who remain at work have lower death rates than their retired peers.
Younger people today mostly accept that they will have to work for longer and that their pensions will be less generous. Employers still need to be persuaded that older workers are worth holding on to. That may be because they have had plenty of younger ones to choose from, partly thanks to the post-war baby-boom and partly because over the past few decades many more women have entered the labour force, increasing employers’ choice. But the reservoir of women able and willing to take up paid work is running low, and the baby-boomers are going grey.
In many countries