The most accurate response to analyze the correlation between Roman expansion policy and trade in the Indian Ocean would be:
As the Romans conquered territory, they gained access to trade resources, which encouraged more expansion.
This statement acknowledges the direct relationship between territorial expansion and the acquisition of valuable trade resources. The Roman Empire's interest in expanding its territories often stemmed from the desire to secure trade routes and access to valuable goods, including spices and textiles available in the Indian Ocean trade network. This expansion not only facilitated trade by providing safe passage and routes for commerce but also served to enhance the empire's economic power by integrating new resources into Roman markets.
The other responses either oversimplify the motivations behind Roman expansion or lack the specific connection to trade in the Indian Ocean, making the selected statement the most robust choice for discussing this correlation.