regional diversity is also called alpha diversity beta diversity gamma diversity ecosystem diversity

The correct answer is 3.
The term gamma diversity (γ-diversity) was introduced by R. H. Whittaker[1] together with the terms alpha diversity (α-diversity) and beta diversity (β-diversity). Whittaker's idea was that the total species diversity in a landscape (γ) is determined by two different things, the mean species diversity in sites or habitats at a more local scale (α) and the differentiation among those habitats (β).