What is the formula of ammonium sulphate? 

(NH₄)₂SO₄

The correct answer is option (NH₄)₂SO₄.

The formula of ammonium sulfate is \( (NH_4)_2SO_4 \).

Ammonium sulfate is an inorganic compound composed of two ammonium ions (\(NH_4^+\)) and one sulfate ion (\(SO_4^{2-}\)). Therefore, the correct formula for ammonium sulfate is \( (NH_4)_2SO_4 \). This compound is commonly used as a fertilizer, flame retardant, and in various industrial applications.