【问题】 He stumbled ____________ the staircase and hurt his leg.·in·to·on·at

He stumbled ____________ the staircase and hurt his leg.·in·to·on·at

正确答案:单选题·on

题目解析:本题出自佳木斯大学,佳木斯大学语言治疗学,由丰阳塔题库搜集整理。