On long standing bleaching powder undergoes autoxidation and forms calcium chlorate and calcium chloride. Hence the correct answer is option (D) i.e. both calcium chlorate and calcium chloride.

What is the effect on long standing of bleaching powder?

On long standing bleaching powder undergoes auto-oxidation to form calcium chloride, CaCl2 and calcium chlorate Ca(ClO3)2.

What happens when bleaching powder is added to water?

Bleaching powder reacts with water to form Calcium Hydroxide or Ca (OH) 2 also called Slaked Lime and Hypochlorous acid (HOC1).