How does public transport help the environment?

Correct answer: It can reduce the number of private vehicles and air pollution

The governing concept is shared, efficient transportation. A bus, metro, or train can carry many passengers in one vehicle, so fewer separate cars or two-wheelers may be required for the same number of journeys. This can reduce fuel use per passenger, traffic congestion, and vehicle-related air pollution, making option D correct. The exact environmental benefit depends on occupancy, vehicle technology, route design, and the energy source, but shared travel generally uses road and fuel resources more efficiently than many individual trips. Options A and C state harmful effects as the main result, while B contradicts the purpose of public transport. It is therefore an important green-transport practice.