A has a definite and unchanging composition. Ex. Salt

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Explanation:

The chemical compound known as DDT with full name is synthesized through the reaction of chlorobenzene with CCl3CHO. It has the molecular weight of 354.49 g/mol, melting point of 108.5°C and boiling point of 260°C.

It is used in the prevention of malaria and pesticide before it was banned in the United States and several other countries as it poses health hazards to animals such as birds and to human beings by affecting the nervous system.

As was used in the eradication of malaria it killed many birds and animals at that time and it was also researched that it is potent and harmful to human beings.