题干
如表是某班同学在正常情况下测得的脉搏1min跳动的次数．
跳动次数 | 55﹣59 | 60﹣64 | 65﹣69 | 70﹣74 | 75﹣79 | 80﹣84 |
人数 | 4 | 6 | 16 | 30 | 4 | 2 |
rider, was found sitting on the bicycle _____ to balance it.