'The' with transport

Let's talk about when we use 'the' with transport.
 

First, we often use the when we are talking about a form of transport as a general idea. We usually do this with public transport (not with cars or bikes) and we usually use verbs such as take, be on, get on and get off:
 

• We took the bus to school.
• She gets off the underground in central London.
• Julie's on the train at the moment.
   

In all of these examples, I'm not talking about a particular bus, train or plane but rather the system of transport as an idea.

However, we use 'no article' when we use a form of transport with by:
 

• We travelled by plane.
• He goes to work by bus.
• We went to Scotland by train.
   

Remember, we can't say 'by foot' or 'by feet' when we're talking about walking. We say 'on foot' (also 'no article').

Let's review!
 

Fill the gap with the or write '-' if we don't need an article.
 

1. We travelled by ______ boat when we went on holiday.
2. Laura is on ______ train.
3. How do you get to work? On ______ foot?