Option 1: Xerxes was not the first to invade India. Xerxes was the ruler of the Persian Empire from 486 to 465 BCE, and his empire did not extend to India at that time.

Option 2: Alexander the Great is known for his conquests, but he was not the first to invade India. He invaded India in 326 BCE, more than a century after the first invasion.

Option 3: Darius-I was the ruler of the Persian Empire from 522 to 486 BCE. He invaded India in 518 BCE, making him the first to invade India among the given options.

Option 4: Seleucus was a general of Alexander the Great and later became a ruler of the Seleucid Empire. He did not invade India himself but engaged in a conflict with the Indian emperor Chandragupta Maurya.

Correct answer: 3. Darius-I was the first to invade India.