The correct option is A Suggest why it might have been argued that the Winters doctrine ought not to apply to pueblo lands.
The author cites the fact that the Rio Grande pueblos were never formally withdrawn from public lands mainly to illustrate the application of the Winters doctrine. He mentions this fact to give reasons why it must be argued that the Winters doctrine should not apply to it. It can be inferred from - "Although, they at that time became part of the United States, the pueblo lands never formally constituted a part of federal public lands; in any event, no treaty, statute, or executive order has ever designated or withdrawn the pueblos from public lands as American Indian reservations. This fact, however, has not barred application of the Winters doctrine." Thus, option A best befits the context.