Lesson 31 - How long does it take? - Exercise 9

Watch the video, then answer the question.
 
There are 2 questions in this exercise. The first question is about prepositions, and the second question is about the title of this lesson.

foot.jpg
On foot
Means of transportation: in general, use by: by car, by bike, by train, by plane, etc., but on foot.
Tap on any word once (mobile), or double-click on any word (computer), to read an English definition.
If you need an approximate translation to your own language, the Google Translate button is available at the top of the screen.