Questions

Gene is a hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism.

In short it is a piece or segment of chromosome.

Genes undergo mutation when their DNA sequence changes. 

Phenol with a molecular formula [C₆H₅OH] is also called as Carbolic Acid. It is a white poisonous clear compound with sweet smell. It is used in making plastics, detergents and drugs.

For a thirsty person, drinking water serves to reduce a drive.

'and made India' should be used to make the sentence grammatically correct. You use 'made' when referring to things already done in the past.'Make' is present and its continuous its still been done unlike 'made' which refers to what has been done

the first country to Recognise 'Orphanage Trafficking' as Slavery is Australia.