Option b is the correct answer. The main purpose of the mansabdari system was to facilitate the recruitment and management of the army. The Mughal army had no regimental structure and the soldiers were not directly recruited by the emperor. Instead, individuals, such as nobles or local leaders, would recruit their own troops, referred to as a mansab, and contribute them to the army. The emperor would assign them a mansab rank based on their merit and loyalty, and pay them accordingly. The emperor would also inspect the troops periodically to ensure their quality and efficiency.