Which foreign invader surrendered his territories to Chandragupta Maurya?

The correct answer is C, Seleucus Nicator. Seleucus was the Macedonian general who took over Alexander's eastern conquests and tried to recover the Indian provinces around 305 BCE. Chandragupta Maurya defeated him, and by the treaty that followed Seleucus gave up the territories of Arachosia, Gedrosia and Paropamisadae, roughly eastern Afghanistan and Baluchistan, in exchange for five hundred elephants. He also sent Megasthenes as his ambassador to the Mauryan court at Pataliputra, and that embassy produced the Indica.

Option A, Menander or Milinda, was an Indo-Greek king of the second century BCE, two centuries later, known for his dialogue with the monk Nagasena in the Milindapanha. Option B, Demosthenes, was an Athenian orator who never came to India. Option D, Gondophernes, was an Indo-Parthian ruler of the first century CE in the north-west. Only Seleucus was a contemporary of Chandragupta Maurya.