Which of the following is NOT a natural radioactive series? MCQ with Answer and Explanation

Explanation:
Rigid PVC (unplasticized, uPVC) is hard, strong, and resistant to chemicals and weathering, making it ideal for pipes, window frames, and fittings. Flexible PVC uses plasticizers. It is not biodegradable. Transparency depends on additives; generally it's translucent. Its chemical resistance is due to the chlorine content.

Explanation:
DAP (diammonium phosphate) contains N (18%) and P₂O₅ (46%). Urea only N; MOP (muriate of potash) only K; SSP only P. NPK mixtures provide all three.

Explanation:
Sulphuric acid (H₂SO₄) is known as the 'King of Chemicals' because of its extensive use in various industries, including fertilizers, dyes, detergents, and petroleum refining. Its production is often considered an indicator of a country's industrial strength and economic development.