What are all the way one can travel from Boston to Philadelphia 
 There are 3 mutually exclusive means of transport.
1. Air
2. Land
3. Sea

Within each option one can list a range of options. For example:
1. Air: take a commercial flight; take a private jet; fly yourself; take a hot air balloon, etc.
2. Land: walk, run, drive, ride a bus, ride a bike, ride a motorcycle, hitch hike, use a roller skate, train, etc.
3. Sea: swim, ride a personal boat, take a commercial boat ride, etc.