根据以下材料，回答题
Middle Age: A Low Point for Most
People around the globe hit the height of their misery and depression in middle 51_________ .， a new international study suggests. The finding by British and American researchers was based on an analysis of well-being among approximately 52_________ million people in 80 nations. With few exceptions，the observation appears to apply across the board， regardless 2 gender （性别） ， culture，geography， wealth， job history， education， and marriage or parental status.
"The scientific fact seems to be that happiness and positive mental health follow a giant "U" 53_________ through life，" said study author Andrew J. Oswald， a professor of economics at Warwick University in Warwickshire， England. "For the average person， it"s high when you"re 20， and then it slowly 54_________ and bottoms out in your 40s. But the good news is that your 55_________ health picks up again， and eventually gets back to the high levels of your youth."
The finding was 56_________ on the pooling of several different sources of happiness data，including: two multi-decade happiness/satisfaction surveys （first launched in the 1970s）， involving about 500，000 American and Western European men and women; four rounds of the 80-nation "World Values Survey" 57_________ between 1981 and 2004 in North America， Eastern and WesternEurope， Asia， Africa， Australia， and Central and South America; and a 2004-2007 survey 58_________ nearly 1 million Britons.
The bottom-line: For most people throughout the world， the highest probability for 59_________ striking is around 44 years of age.
In the United States， however， some as-yet unexplained 60_________ differences were observed， with happiness among men dipping the most in their early 50s， whereas women hit their nadir （最低点 ） around the age of 40.
The researchers cautioned that cheerful people tend to live longer than unhappy. 61_________ – a fact that might have skewed （使偏斜） the overall finding. But they also suggested that evidence of a happiness 62_________ might simply reflect a midlife choice to give up long-held but no longer tenable （守得住的） aspiration （志向）， followed by a senior"s sense of gratitude for having successfully endured 63_________ others did not.
"That said， some might find it helpful simply to understand the general 64_________ of mental health as they go through their own life，" said Oswald. "It might be useful for people to realize that if they are 65_________ in their 40s this is normal. It is not exceptional. And just knowing this might help".
回答（51）题 查看材料

A. age
B. place
C. height
D. degree