The correct option is C CaSO4
The given chemical equation depicts the reaction between bleaching powder (calcium oxychloride) and dilute sulphuric acid. The calcium oxychloride (CaOCl2) reacts with dilute sulphuric acid (H2SO4) to form calcium sulphate (CaSO4), chlorine gas (Cl2) along with water (H2O). So, P is CaSO4.