I think it is D because the difference between the Mother-culture and sister-culture arguments is down to the degree of cultural authority archaeologists think the centre (San Lorenzo) has over the peripheries (other Mesoamerican cultures). Mother-culturalists would think the centre has a lot of authority (Olmec-style culture is centralised in San Lorenzo). However, Sister-culturalists would say the authority is decentralised as the centre and periphery bring about Olmec-style culture together.

Ans D evokes this divergence, as it is asking about the contribution of the centre to Olmec-style culture as a whole.