Final answer:
Attila the Hun did not attack Constantinople because he died in 453 AD, the city was heavily fortified, and the Eastern Roman Empire could raise a large army to defend it. The correct answer is (D) All of the above.
Step-by-step explanation:
The reasons why Attila the Hun never attacked Constantinople are multifaceted. Firstly, Attila died in 453 AD, which was before he could launch an attack on the city. In addition to this, Constantinople was heavily fortified with strong defensive walls that had protected the city for centuries, making it a formidable challenge to any invader. Also, the Eastern Roman Empire possessed the capability to raise a large army for the city's defense, which played a crucial role in deterring Attila's plans. Therefore, the correct answer to the question would be (D) All of the above.