The answer is they had no written records.
This option is not correct because there is no substantial evidence to suggest that Sechin Bajo and Caral were ruled by monarchies. The political structures of these early Peruvian sites are not well-documented, and it is not clear if they had centralized monarchies similar to those in Mesopotamia, Egypt, India, and China.
While trade was certainly a part of these civilizations, it was not the defining characteristic that set them apart from Mesopotamia, Egypt, India, and China. These other civilizations were also heavily influenced by trade routes.
This option is incorrect because both Sechin Bajo and Caral are known for their monumental architecture. Caral, for example, features large pyramidal structures and plazas, indicating a complex society capable of significant architectural achievements.
This is the correct answer. Unlike the civilizations of Mesopotamia, Egypt, India, and China, which all developed forms of writing, the early Peruvian sites of Sechin Bajo and Caral did not leave behind written records. This lack of written documentation is a significant difference between these Andean civilizations and their Old World counterparts.