Answer:
A) The high cost of defending the empire
Explanation:
At its height Roman empire stretched from middle est to Atlantic ocean. It was not easy to govern such a vast territory and due to its vastness the empire faced logistical and administrative issues.
Although it had excellent road systems, the Romans were still unable to effectively manage it territories. It had to struggle to maintain enough resources and troops to defend itself from rebellions and outside attacks. Emperor Hadrian even constructed wall in Britain to keep the enemies away.
As more money was spent on the military maintain the empire it affected the technological advancement. Excess expenditure on the army was one of the many reasons for the downfall of Roman empire.
