Ashoka sent his son Mahendra to which of the following neighbouring countries to propagate Buddhism in ancient India?

Emperor Ashoka made significant efforts to propagate Buddhism outside the boundaries of his empire. After the Third Buddhist Council, he sent Buddhist missions (Dhammadutas) to various regions. He sent his son Mahendra (Mahinda) and daughter Sanghamitra (Sanghamitta) to Sri Lanka (then known as Ceylon or Tambapanni) to spread the teachings of Buddhism during the reign of King Devanampiya Tissa.