The correct answer is: a) Saka (Scythian).
The Sakas were a nomadic people of Iranian origin who migrated to India in the 2nd century BCE. They established a number of kingdoms in the northwestern part of the subcontinent, including the Kshatrapa dynasty, which ruled Gujarat for centuries.
The Kushans were a nomadic people of Central Asian origin who invaded India in the 1st century CE. They established a large empire that stretched from Afghanistan to Pakistan and northern India.
The Parthians were a nomadic people of Iranian origin who ruled Persia from the 3rd century BCE to the 3rd century CE. They were a major power in the region and were often at war with the Roman Empire.
The Greeks were a people of European origin who invaded India in the 4th century BCE. They established a number of kingdoms in the northwestern part of the subcontinent, including the Indo-Greek Kingdom, which ruled parts of Pakistan and northwestern India.
The Kshatrapas were a dynasty of Saka (Scythian) origin that ruled Gujarat and parts of northwestern India from the 2nd century BCE to the 4th century CE. They were initially vassals of the Kushan Empire, but they later became independent. The Kshatrapas were a powerful dynasty and they played an important role in the history of Gujarat.