Read the following passage and mark the letter A, B, C, or D to indicate the correct answer that best fits each of the numbered blanks.

Public transport

Some people drive to work every day while many others use some form of public transport. This may (21) ___________ buses, subways, and trains. Many people from the suburbs use a combination of these methods of public transit. In most public bus systems, people (22) ___________ use either a ticket or cash for their bus fare. In some cities, bus drivers will not make change so riders need to have the exact fare. Many public transit users buy monthly bus passes (23) ___________ they are cheaper and more convenient.

It is often necessary for riders to change buses when traveling to their (24) ___________. If they have to change to another bus, they must ask the driver for a bus transfer when they first board the bus. This paper marks the time, date, and bus route they are using. The bus transfer is only valid (25) ___________ a certain period of time. The rider must give the transfer to the driver of the connecting bus.

This may (21) ___________ buses, subways, and trains