People around the globe hit the height of their misery and depression in (51) age, a new international study suggests.The finding by British and American researchers was based on an analysis of well-being among approximately 2 million people in 80 nations. With few exceptions, the observation appears to apply across the board, regardless (52) gender, 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 falls and bottoms out (54) your 40s. But the good news is that your (55) health picks up again, and eventually gets back to the high levels of our 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 Western Europe, 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 depression striking is around 44 years of (59) .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 around the age of 40.The researchers cautioned that cheerful people tend to live longer than unhappy (61) —a fact that might have skewed 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 aspirations, 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. " 55.（）

A. mental
B. good
C. general
D. physical