Osman was the leader of a Muslim empire ordered a new code of laws for his empire and oversaw construction of a stunning mosque in the capital at Istanbul. The correct option in regards to the given question is option "A". Osman was the founder of the Ottoman Empire.Sultan Mehmed II conquered Istanbul in 1453 and it laid the foundation of a great empire. Istanbul was then named as Constantinople. After Osman died the expansion of the Ottoman empire did not stop, it went on continuing with the expansion. Orhan was the son of Osman and he changed the capital of the Ottoman empire from Constantinople to Bursa after conquering it.