单项选择题

Children have been said to have brain-injured child syndrome, hyperactive (极度活跃的) child syndrome and attention-deficit disorder (ADD). As early as the 1940’s, psychiatrists have (67) children with hyperactivity and extremely distracted and impulsive (冲动的). These frequent name changes show how (68) researchers, are about the causes (69) the problem and the diagnostic criteria for the disorders. In the past several years, the people who (70) attention deficit hyperactivity disorder (ADHD) have (71) to clarify the disorder’s causes and (72) , and have reasons to believe that it may be genetic. Today’s view (73) this disorder is very different from the beliefs of just a few years ago. Researchers are finding that ADHD is not a disorder of just attention, but is from a developmental (74) in the brain’s circuitry and self-control. The loss of self-control (75) other important brain functions mandatory for maintaining (76) . ADHD involves two sets of symptoms: inattention and a (77) of hyperactive and impulsive behaviors. Most children are more active and distractive than adults are. Children are more inconsistent, affected by brief actions. The younger the child, the less (78) they are. This behavior is a (79) of a problem when it is displayed more in them than in their (80) . Boys are at least three times more (81) than girls to have ADHD. Studies have found that ADHD in boys outnumbers girls 9 to 1, this is because boys are genetically likely to (82) disorders in the nervous system. These behaviors generally (83) between the ages of 3 and 5. (84) , some children don’t start to develop the disorder until (85) childhood or early adolescence. Researchers are unable to find the reasons for this (86) .