Which one of the following fuels causes minimum environmental pollution ?

Hydrogen is the least polluting option because when used in fuel-cell vehicles it produces near‑zero tailpipe emissions—essentially only water vapor (and negligible CO2)—unlike fossil fuels that emit particulates, NOx, SOx and CO2. Textbook evidence states fuel‑cell powered vehicles have very high energy conversion efficiency and near‑zero pollution, with CO2 and water vapor being the only emissions; it also highlights that diesel buses emit significant SPM and SO2 [1]. Official technical guidance confirms hydrogen fuel‑cell electric vehicles emit none of the harmful combustion pollutants (only water and warm air), and hydrogen use in internal combustion engines still produces far lower conventional pollutants than coal, diesel or kerosene combustions in typical use [2].

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 22: Renewable Energy > Fuel cells for automobile transport > p. 296
2. [2] https://afdc.energy.gov/fuels/hydrogen-benefits