Question

Lucy and Lily go to school ________ every day．

1. A.
   on foot
2. B.
   on the foot
3. C.
   by my bike
4. D.
   on the feet

Answer 1

A
“步行”on foot的foot不变为复数feet, on和foot之间也没有任何修饰词。“骑自行车”用by bike，中间也不加任何修饰词。