We rarely perceive more than a minute（ ）of the sights and sounds that fall upon our sense organs; the great majority pass us by.

A.fiction B.function C.fraction D.friction

s="" guess.="" but="" the="" driving="" forces="" behind="" ageing="" and="" population="" decline,="" how="" birthrate="" longer="" life="" expectancy="" seem="" fairly="" fixed.Only the United States, with higher birthrates and immigration, escapes population decline. But even in the United States, there are fewer potential workers for each potential retiree. As long as retirees are supported by taxpayers, through Social security and health insurance, the economic burden on workers will rise. In most countries, the shift would be stark and possibly unworkable. Germany's working age population is projected to drop from 51 million in 2000 to 29 million in 2050, meanwhile, the 65 and over population in the more developed countries has essentially ceased.Americans may have succeeded better in mixing family and work. Or immigrants may have more children than other Americans. Regardless, all rich nations will feel the pressures of aging---or declining populations. And there is a perverse possibility that more old people will further reduce the. number of young people. If taxes on workers increase to cover higher retirement benefits, family's willingness to have children may diminish, because it would be harder to pay for them. Immigration is one possible safety value. But for Europe and Japan, the-increase needed to avert population declines would be huge,Richer countries could also prepare for their aging by investing in poorer countries. Trade could substitute for immigration investment from wealthier countries would enable developing nations to build up their industries. As people retire in the rich world, they could use some of the dividends and interest from their investments to buy imports from poorer countries.To predict the future is not always easy. But few rich countries are anticipating it. They should be tempering the vicious circle of higher retirement spending, heavier taxes on workers and fewer children. This means gradually raising retirement age. And scaling back benefits, especially for wealthier retirees. '1.The declining population in rich countries will mainly cause（ ）.2.The loss population in rich countries is directly due to （ ）.3.Aging will bring a new round of population decline because （ ）.4.One way to get enough money to feed the aging generation is to（ ）.'>

During the next half-century, most wealthy societies, the United States is a conspicuous exception, will lose population; all will have older populations. This is a collective change that will profoundly influence the world economy, the future of democracy and relations between nations with declining populations (generally richer countries) and those will expanding populations (general poorer countries). Just how the effect might be is anyone's guess. But the driving forces behind ageing and population decline, how birthrate and longer life expectancy seem fairly fixed.Only the United States, with higher birthrates and immigration, escapes population decline. But even in the United States, there are fewer potential workers for each potential retiree. As long as retirees are supported by taxpayers, through Social security and health insurance, the economic burden on workers will rise. In most countries, the shift would be stark and possibly unworkable. Germany's working age population is projected to drop from 51 million in 2000 to 29 million in 2050, meanwhile, the 65 and over population in the more developed countries has essentially ceased.Americans may have succeeded better in mixing family and work. Or immigrants may have more children than other Americans. Regardless, all rich nations will feel the pressures of aging---or declining populations. And there is a perverse possibility that more old people will further reduce the. number of young people. If taxes on workers increase to cover higher retirement benefits, family's willingness to have children may diminish, because it would be harder to pay for them. Immigration is one possible safety value. But for Europe and Japan, the-increase needed to avert population declines would be hug

As a general rule, Dad is generous, but as a merchant, he usually drives a hard（ ）.

A.bargain B.deal C.transaction D.negotiation

His inability to learn foreign language was an （ ）to his career.

A.shortage B.disturbance C.occurrence D.obstacle

Based on the（ ）that every business is now free to formulate its own strategy in light of the changing market, I would predict a market improvement in the efficiency of Chinas economy.

A.guidance B.instruction C.premise D.eminence

All the flights（ ） because of the snowstorm, we had to take the train instead.

A.were canceled B.had been canceled C.having canceled D.having been canceled