Water is considered as a compound of hydrogen and oxygen and not a mixture of hydrogen and oxygen and comment on it

Wat is considered a compound of hydrogen and oxygen and not a mixture because hydrogen and oxygen have gone through a chemical process to form the compound h2O. A mixture can generally be easily separated whereas a compound must undergo another chemical process to separate its elements. Therefore to separate oxygen and hydrogen from water a chemical process is necessary. 

The answer options is d

No table found. the question asks for covalent bond based on electronegativies