More Americans are opting to work well into retirement, a growing trend that threat-ens to upend the old workforce model.

One in three Americans who are at least 40 have or plan to have a job in retirement to prepare for a longer life, according to a survey conducted by Harris Poll for TD Ameri-trade. Even more surprising is that more than half of "unretirees"-those who plan to work in retirement or went back to work after retiring-said they would be employed in their later years even if they had enough money to settle down, the survey showed.

Financial needs aren't the only culprit for the "unretirement" trend. Other reasons,according to the study, include personal fulfillment such as staying mentally fit, preven-ting boredom or avoidling depression.

"The concept of retirement is evolving," said Christine Russell, senior manager of retirement at TD Ameritrade. "It's not just about finances. The value of work is also driving folks to continue working past retirement.”

One reason for the change in retirement patterns: Americans are living longer. O1-der Americans are also the fastest-growing segment of the U.S. workforce, and boomers are expected to live longer than previous generations. The percentage of retirement-age people in the labor force has doubled over the past three decades. About 20% of people 65 and older were in the workforce in February, up from an all-time low of 10% in Janu-ary 1985, according to money manager United Income.

Because of longer life spans, Americans are also boosting their savings to preserve their nest eggs, the TD Ameritrade study showed, which surveyed 2,000 adults between 40 to 79. Six in 10 "unretires" are increasing their savings in anticipation of a longer life, according to the survey. Among the most popular ways they are doing this, the company said, is by reducing their overall expenses, securing life insurance or maximi-zing their contributions to retirement accounts.

Unfortunately, many people who are opting to work in retirement are preparing to do so because they are worried about making ends meet in their later years, said Brent Weiss, a co-founder at Baltimore-based financial-planning firm Facet Wealth. He sug-gested that preretirees should speak with a financial adviser to set long-term financial goals.

"The most challenging moments in life are getting married, starting a family and ul-timately retiring," Weiss said. "It's not just a financial decision, but an emotional one.Many people believe they can't retire."

1.The survey conducted by Harris Poll indicates that          ·

[A]over half of the retirees are physically fit for work

[B] the old workforceis as active as the younger one

[C]one in three Americans enjoy earlier retirement

[D]more Americans are willing to work in retirement

2.It can be inferred from Paragraph 3 that Americans tend to think that          

[A]retirement may cause problems for them

[B] boredom can be relieved after retirement

[C] the mental health of retirees is overlooked

[D]“unretirement” contributes to the economy 

3. Retirement patterns are changing partly due to           

[A]labor shortage

[B]population growth

[C]longer life expectancy

[D]rising living costs

4.Many "unretirees”are increasing their savings by           

[A]investing more in stocks

[B]taking up odd jobs

[C] getting well-paid work

[D]spending less

5. With regard to retirement, Brent Weiss thinks that many people are          

[A] unprepared

[B] unafraid

[C] disappointed

[D]enthusiastic