The right answers are "different ethnic backgrounds", "educational or occupational differences" and "geographical differences within a state".
Here is a brief explanation on this:
Language is dynamic and subject to numerous variations. This peculiarity of each and every language is what we call linguistic variation, which is subject to the historical, geographical and sociocultural context in which the speakers are integrated.
This plurality of language is easily observed in Brazil, a country of significant territorial extension and cultural multiplicity. Linguistic variations occur because, since the primary function of language is communication, speakers arrange and rearrange language according to the need for social interaction.
