The correct answer is C. Oxides of sulphur.

Acid rain is formed when pollutants in the atmosphere, such as sulphur dioxide (SO₂) and nitrogen oxides (NOx), react with water, oxygen, and other chemicals to form acidic compounds. These compounds can then fall to the ground as precipitation, resulting in acid rain.

Sulphur dioxide (SO₂) is a major contributor to acid rain. When SO₂ is released into the atmosphere, it can react with water and oxygen to form sulphuric acid (H₂SO₄), which is a strong acid:

SO₂ + H₂O + 1/2O₂ → H₂SO₄

The other options are not directly responsible for acid rain:

A. Oxides of lead are toxic pollutants, but they don't contribute to acid rain.

B. Particulate matter can be a pollutant, but it's not directly involved in acid rain formation.

D. Gaseous hydrocarbons can contribute to smog and other air quality issues, but they're not a primary cause of acid rain.