Option d is the correct answer. The Gupta Empire was not affected by the Arab invasion, which occurred in the 7 th and 8 th centuries CE, after the decline of the Gupta Empire. The Arab invasion mainly targeted the regions of Sindh and Multan, which were ruled by the Brahmanas and the Rai dynasty respectively. Important Tips The Gupta Empire, on the other hand, was weakened by the following factors: Huna invasion: They challenged the authority of the Gupta emperors, especially Skandagupta, who fought bravely against them but could not stop their advance. Feudal set-up of administration: The Gupta Empire had a decentralized system of administration, where the local governors and feudal lords enjoyed a high degree of autonomy and power. This led to the fragmentation and disintegration of the Gupta Empire, as the loyalty and allegiance of these subordinates to the central authority declined over time Acceptance of Buddhism by the later Guptas: The later Guptas, who ruled over Magadha and Bengal after the collapse of the main Gupta dynasty, were influenced by Buddhism and patronized Buddhist institutions. This alienated them from the Hindu majority of their subjects, who were loyal to the earlier Guptas, who were devout followers of Vaishnavism. This also weakened their political and military strength, as they faced opposition from Hindu revivalist movements and foreign invaders.