Final answer:
Native Americans were primarily exposed to white people's culture through trade, where they acquired various goods and practices. The correct option is (a) through trade, they acquired goods that the white people used in their lives.
Step-by-step explanation:
The primary way Native Americans were exposed to white people's culture before the passage of the Indian Removal Act was through trade with the settlers. Through trade, Native Americans acquired goods that were used in the everyday life of white settlers. These interactions provided an avenue for cultural exchange and the introduction of European goods and practices into Native American communities.
While there may have been other ways in which Native Americans were exposed to white culture, such as through protection arrangements or inter-tribal interactions, trade was a consistent and widespread method for cultural exchange. The correct option is (a) through trade, they acquired goods that the white people used in their lives.