题目内容：
根据以下材料，回答题Young Adults Who Exercise Get Higher IQ Scores
Young adults who are fit have a higher IQ and are more 51_________ to go on to university, reveals a major new study carried out at the Sahlgrenska Academy and Sahlgrenska University Hospital.
The results were recently published in the Proceedings of the National Academy of Sciences (PNAS). The study involved 1.2 million Swedish men doing military service who were born between 1950 and 1976. The research group analysed the 52_________ of both physical and IQ tests the youngsters took fight after they started serving the army.
The study shows a clear link 53_________ good physical fitness and better results for the IQ test. The strongest links are for 54_________ thinking and verbal comprehension. But it is only fitness that plays a 55_________ in the results for the IQ test, and not strength. "Being fit means that you also have good heart and lung 56_________ and that your brain gets plenty of 57_________," says Michael Nilsson, professor at the Sahlgrenska Academy and chief physician at the Sahlgrenska University Hospital. "This may be one of the reasons 58_________ we can see a clear link with fitness, but not with muscular 59_________. We are also seeing that there are growth factors that are important. "
By analysing data for twins, the researchers have been 60_________ to determine that it is primarily environmental factors and not genes that explain the link between fitness and a 61_________ IQ.
"We have also shown that those youngsters who 62_________ their physical fitness between ages of 15 and 18 increase their cognitive performance," says Mafia Aberg, researcher at the Sahlgrenska Academy and physician at Aby health centre. "This being the case, physical 63_________ is a subject that has an important place in schools, and is an absolute must if we want to do well in maths and other theoretical subjects."
The researchers have also compared the results from fitness tests 64_________ national service with the socio-economic status of the men later in 65_________. Those who were fit at I 8 were more likely to go into higher education, and many secured more qualified jobs.
回答(51)题 A．carefully
B．secretly
C．likely
D．happily
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