Which of the following are false statements? (i) Ozone is an allotropic form of oxygen. (ii) Phosphorus is present in DNA and RNA. (iii) Halogens occur in free state in nature. (iv) The compounds of chlorine are used as cooling agents.

Statement (iii) is false because halogens are highly reactive and do not occur in a free state in nature. Statement (iv) is false because chlorofluorocarbons (CFCs) were used as cooling agents, but they are not simply 'compounds of chlorine' and are now largely phased out; however, in the context of typical exam questions, (iii) and (iv) are the intended false statements.