How does this account differ from the Christian account?

It differs totally as for Ottomans (Muslims) they are deliberating the city, while the Byzantines (Christians) believe that they have been conquered by the infidels.

Of course, this source shows the greatness of Ottoman cause, while Christians believe that they have come to destroy and butcher them.

Explanation:

Fall of Constantinople is one of the events that marks the end of Middle Ages.

It marked the end of Byzantine Empire, that lasted for more than thousand years, while on the other side, as it is said in this document it opened the door for Muslim invasion in Europe.

While for the Byzantines it was the end, for Ottomans was the beginning of new era.

the answer is a. since they were a huge producer of cotton and wanted the most money for it.