Reduction in the usage of fossil fuels can be brought about bya.using alternative energy sourcesb.reducing car taxesc.changing lifestylesd.encouraging the use of mass transport systems such as buses and railways

The reduction in the usage of fossil fuels can be brought about by:

a. Using alternative energy sources: This involves shifting from fossil fuels to renewable energy sources such as solar, wind, hydro, and geothermal energy. These sources are sustainable and do not deplete natural resources.

b. Reducing car taxes: This option might not directly contribute to the reduction of fossil fuel usage. While it could potentially encourage more people to own cars, it doesn't necessarily mean they will choose more fuel-efficient or electric vehicles. Therefore, this might not be the most effective method.

c. Changing lifestyles: This can have a significant impact on reducing fossil fuel usage. Simple changes like choosing to walk or bike for short distances instead of driving, using energy-efficient appliances, and reducing consumption can all contribute to less reliance on fossil fuels.

d. Encouraging the use of mass transport systems such as buses and railways: Public transportation is much more fuel-efficient than individual car ownership. By using buses, trams, trains, and other forms of public transport, we can significantly reduce the amount of fossil fuels used for transportation.

In conclusion, while all these methods can contribute to reducing fossil fuel usage, some (like using alternative energy sources, changing lifestyles, and encouraging the use of mass transport systems) are likely to be more effective than others (like reducing car taxes).