Article: Theravada ("Doctrine of the Elders", or "Ancient Doctrine") is the oldest surviving Buddhist school. It is relatively conservative, and generally closest to early Buddhism. The name Theravāda comes from the ancestral Sthāvirīya, one of the early Buddhist schools, from which the Theravadins claim descent. After unsuccessfully trying to modify the Vinaya, a small group of "elderly members", i.e. sthaviras, broke away from the majority Mahāsāṃghika during the Second Buddhist council, giving rise to the Sthavira sect. Sinhalese Buddhist reformers in the late nineteenth and early twentieth centuries portrayed the Pali Canon as the original version of scripture. They also emphasized Theravada being rational and scientific.

Question: What is the oldest surviving Buddhist school?
Theravada