Answer:
As per Gerstel and Sarkisian, the social class is more significant than ethnicity to understand the dissimilarities between family ties as well as the behavior of ethnic groups. <em>To substantiate their claim, they have compared the distinct ethnic groups and developed a database that helped in examining the distinctions in the practical, financial, and emotional relationships of each group and this also supported their claim</em>. It contains critical distinction to the authors because their assumptions lack a universal approach and apply to certain conditions.
Most wild birds feed themselves with fruit from trees, and killing insects that they hunt.
The usage if vast in this passage means large, therefore the answer is A.
