题目内容：
Questionsare based on the following passage.Those baby-faced people now have another reason to be smug (自鸣得意的 ): a new Danish study says looking young 47 means a longer life. Research suggests that people who look younger than their years also live longer.
In 2001, Danish researchers 48 physical and cognitive tests on more than 1,800 pairs of twins over aged 70, as well as taking photos of their faces. Three groups of people who didn't know the twins' real ages guessed how old they were. The researchers then 49 how long the twins 50 over 7 years.
The experts found that people who looked younger than their 51 age were far more likely to survive, even after they 52 for other factors like gender and environment. The bigger the difference in 53 age within any twin pair, the more likely it was that the older-looking twin died first.
They also found a possible biological 54 _: people who looked younger also tended to have longer telomeres (端粒), a key DNA. 55 that is linked to aging. People with shorter telomeres are thought to age faster. In the Danish study, the more fresh-faced people had longer telomeres.
The authors said that perceived age, which is widely used by doctors as a general 56 of a patient's health, is a good biomarker of aging that predicts survival among people over age 70.
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