你没有给出一个语境 例如:
A:How do you go to school?(或者再加一个频度词)
B:(二楼的正确)
或:
A:How did you go to school yesterday?
B:(一楼的可以 但是我认为 I went to school on foot. 更好)
所以您的这个问题有两个答案 能不能再补充一下问题呢
I was walking to school
I go to school by walk
i'm walking to school
I go to school on foot