The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
We can say that the people in the post-Mauryan periods had trade relations with distant lands because they were people dedicated to farming the land and developed good agriculture techniques that made them produce good cash crops that were traded to faraway places like Europe.
These long-distance trade routes served also to trade crafts and pieces of art. South Indian people could create routes by land through the river valleys. Post-Mauryan people learn how to navigate the Arabian Sea to create navigation routes to other distant places.