The most accurate response in analyzing the correlation between Roman expansion policy and trade in the Indian Ocean is: "As the Romans conquered territory, they gained access to trade resources, which encouraged more expansion."
This statement reflects the reality that Roman expansion was often motivated by the desire to secure trade routes and resources. The Romans recognized the economic benefits of controlling trade networks, which allowed them to access valuable goods from the East, such as spices, silk, and precious metals. Consequently, territorial expansion was not only a strategy for political dominance but also a means to enhance their economic power through trade.
While aspects of the other responses touch on related concepts, they either lack nuance or misrepresent the broader context of Roman motivations for expansion. For example, while the Romans may have sought to protect their interests and, at times, punished civilizations that refused to trade, these actions connected back to their overall economic strategy. Thus, the relationship between their expansion and trade was indeed reciprocal, reinforcing the importance of trade in their imperial policy.