Explanation

A is correct because Ammonium Nitrate (NH₄NO₃) was the explosive material involved in the Beirut blast. B is incorrect because Sodium Hypochlorite or Sodium Chlorate are not the primary substance cited for this explosion. C is incorrect because Cygnite (C₂N₁₄) is a different chemical compound and was not the cause. D is incorrect because option A provides the specific chemical responsible.