What led to the final decline and fall of the otttamen empire?

What led to the fall of Ottoman Empire?

1. Suleiman the Magnificent led Ottoman army on Conquest in Central Europe. Failed siege of Vienna marks the end of Ottoman conquest in central Europe
2. A combined Spanish and Italian fleet defeated Ottoman navy at Lepanto in Mediterranean Sea. This ended Ottoman’s dominance in the sea.
3. Conservative, religious and political views arise
4. Sultans after Suleiman were weak and corrupt.
5. Nationalist feelings arise in the millets and other territories

The Ottoman Empire was one of the largest empires of the history. It lasted for several hundred years. The Ottoman Empire reached its peak during the reign of Suleiman who ruled from 1520 - 1566. The empire began to decline after its defeat in year 1571 in the battle of Lepanto when it lost almost all of its navy. 
In the 17th century, European power began to grow, at the expense of Ottoman power, which had encroached into Europe in the 16th century.  The Ottomans lost the Battle of Vienna in 1683, a sign of their waning status in respect to European power.  Over the next century or more, the Ottomans began losing portions of their far flung empire, which had been hard to maintain.  Weak leadership in the Ottoman central government was part of the problem, as was the rising movement of nationalism in the 18th century. For instance, Greece established its independence from the Ottomans in a nationalistic revolt in the 1830s.  

By the beginning of the 20th century, the Ottoman Empire was known as "the sick man of Europe," and European powers were eager to take over their territory if and when the Ottomans fell.  The Ottoman Empire joined the losing side in World War I, and after that war the empire ceased to exist.  Turkey itself remained as the seat of Turkish power, and mandate governments by the victorious powers in World War I, such as Britain and France, were set up over former Ottoman territories. 

The answer to the question is a.