Medium
Choose the correct statements regarding fuels: (i) Fuels liberate heat on burning (ii) CNG is less polluting than petrol and diesel (iii) CNG is a non-conventional source of energy (iv) Coal is formed from plant remains
Explanation
Explanation
Fuels do liberate heat on burning, CNG is indeed less polluting than petrol/diesel, and coal is formed from plant remains, so (i), (ii) and (iv) are true. However, CNG is a conventional (fossil-fuel based) source of energy, not non-conventional, making statement (iii) false.
PRO TIP
Re-check your working by substituting the answer back into the original question.