The correct answer is - D. Controlled trade routes between Asia and Europe.
The Ottomans during the 16th century had already established a vast empire, an empire with excellent strategic location where they were right in the middle of the extremely important trade routes between Asia and Europe.
The goods that were being exchanges between the two continents all had to go through the Ottoman territory in order to reach their final destination. The Ottomans saw a great opportunity to make huge wealth out of the situation, so they imposed taxes for literally every trade good that was passing through their territory, so in no time the empire became very wealthy.