【单选题】

The author's main purpose is to______.
A．criticize the emphasis on social standing in discussion of the assimilation of Puerto Ricans in the United States

B．support the thesis that assimilation has not been a benign process for Puerto Ricans
C．defend a view of the assimilation of Puerto Ri, cans that emphasizes the preservation of national culture
D．indicate deficiencies in two schools of thought on the assimilation of Puerto Ricans in the United States