The correct answer is option 4: 1, 2 and 3.

1. Ashvaghosa: He was a Buddhist philosopher and poet. Ashvaghosa was a contemporary of Kanishka, the Kushan emperor. He is known for his literary works, especially the famous play "Buddhacharita," which chronicles the life of Buddha.

2. Nagarjuna: He was a prominent Buddhist philosopher and founder of the Madhyamaka school of Mahayana Buddhism. Nagarjuna lived during the same time period as Kanishka and is recognized as one of the most important figures in the development of Mahayana Buddhist philosophy.

3. Vasumitra: He was a Buddhist scholar and leader of the Sarvastivada school of Buddhism. Vasumitra also lived during the same era as Kanishka and was involved in the compilation of Buddhist scriptures and teachings.

4. Chanakya: Although a great scholar and advisor, Chanakya was not a contemporary of Kanishka. Chanakya, also known as Kautilya or Vishnugupta, was an influential figure in ancient India and served as the chief advisor to Chandragupta Maurya, the founder of the Ma