Answer:
Correct answer is It was a peninsula, with 2 rings of thick walls surrounded by a moat, which made it easier to defend than Rome.
Explanation:
First option is not correct as Constantinople is located on Bosporus, not on Persian Gulf.
Last option is not correct a these religious orders were created during the Crusades and Constantinople was created centuries before that.
Second option is correct as Constantinople was protected from three sides by water and the city walls enabled the defense of city, which fell only twice throughout history.