Who among the following were the first to invade india ?

Arabs were the first to invade India. 

The initial encounter of the Hindu rulers of Sindh started in 636, while under the leadership of Hakam, Caliph Umar ibn al-Khattab occupied India against Thane and Bharuch.

A number of Arab invasions have taken place Indian states after that.

The invasion of Mohammed Bin Qasim in 712 AD was important in this sense.

With a cavalry of about 8000, he invaded Sindh.

In the later decades, on the other hand, invasions by Afghans, Mongols and Turks occurred.

Hence, the correct answer is option C, Arabs.