<Tr> <Th> (19) Vietnam </Th> <Td> 37 </Td> </Tr> <Tr> <Th> (20) Iran </Th> <Td> 36 </Td> </Tr> <Tr> <Td_colspan="10"> <P> The twenty largest countries by agricultural output in 2015, according to the IMF and CIA World Factbook . </P> </Td> </Tr> <P> The twenty largest countries by agricultural output in 2015, according to the IMF and CIA World Factbook . </P>

Which of the following categories is considered part of the primary sector of the social structure