48. Which of the following sentence can be added to the end of the last paragraph without disrupting the flow of the whole passage? (A) The above research finding thus provides convincing evidence that we are hardwired to be overly sensitive to changes in terrain slope. (B) A wealth of evidence has shown that people verbally overestimate the slant of hills by 15° to 20°. (C) Maybe people tend to overestimate the steepness of slopes and not because they are lazy. (D) Thus, the evidence favoring a psychological explanation has been disputed.