Why is Mecca a trade center for the Arabian peninsula?

Because Mecca became the center of a loose confederation of client tribes, which included those of the Banu Tamim. Other regional powers such as the Abyssinian, Ghassan, and Lakhm were in decline, leaving Meccan trade to be the primary binding force in Arabia in the late 6th century.

interdependence is when all participating groups and individuals depend on each other. if you depend on one anothers goods, you end up trading in order to get the items you're looking for. (for ex: if i have food and you have water, we trade in order to depend on each other to live)

your answer will most likely be a.