Passage One Questions 21 to 25 are based on the following passage. Each summer, no matter how pressing my work schedule, I take off one day exclusively for my son. We call it dad-son day. This year our third stop was the amusement park, where be discovered that he was tall enough to ride one of the fastest roller coasters (过山车) in the world. We blasted through face-stretching turns and loops for ninety seconds. Then, as we stepped off the ride, be shrugged and, in a distressingly calm voice, remarked that it was not as exciting as other rides he’d been on. As I listened, I began to sense something seriously out of balance. Throughout the season, I noticed similar events all around me. Parents seemed hard pressed to find new thrills for indifferent kids. Surrounded by ever-greater stimulation, their young faces were looking disappointed and bored. Facing their children’s complaints of “nothing to do“, parents were shelling out large numbers of dollars for various forms of entertainment. In many cases the money seemed to do little more than buy transient relief from the terrible moans of their bored children. This set me pondering the obvious question:“ How can it be so hard for kids to find something to do when there’s never been such a range of stimulating entertainment available to them?” What really worries me is the intensity of the stimulation. I watch my little daughter’s face as she absorbs the powerful onslaught (冲击) of arousing visuals and bloody special effects in movies. Why do children immersed in this much excitement seem starved for more? That was, I realized, the point. I discovered during my own reckless adolescence that what creates excitement is not going fast, but going faster. Thrills have less to do with speed than changes in speed. I’m concerned about the cumulative effect of years at these levels of feverish activity. It is no mystery to me why many teenagers appear apathetic (麻木的) and burned out, with a “been there, done that” air of indifference toward much of life. As increasing numbers of friends’ children are prescribed medications-stimulants to deal with inattentiveness at school or anti-depressants to help with the loss of interest and joy in their lives-I question the role of kids’ boredom in some of the diagnoses. My own work is focused on the chemical imbalances and biological factors related to behavioral and emotional disorders. These are complex problems. Yet I’ve been reflecting more and more on how the pace of life and the intensity of stimulation may be contributing to the rising rates of psychiatric problems among children and adolescents in our society. 21. The author tell surprised in the amusement park at fact that ________. A) his son was not as thrilled by the roller coasters ride as expected B) his son blasted through the turns and loops with his face stretched C) his son appeared distressed but calm while riding the roller coasters D) his son could keep his balance so well on the fast moving roller coasters（A）