Whose teachings have been assembled in 3 collections called Tripitaka?
A. Makhkhali Goshala
B. Vardhamana Mahavira
C. Ajita Keshkambalin
D. Gautam Buddha.

Hint: During his lifespan, he taught in Vedic Sanskrit, which became unintelligible to the people. In his Indian dialect, he also encouraged his monks to propagate his teachings in the vernacular. It was composed between about \[550\]BC.

Complete answer:
It is the traditional term for the Buddhist scriptures. His teachings came to be known as Buddhism. It is also known as Pali Canon in English. Its main divisions, called Pitakas. His teachings and at the same time his followers have been compiled in three collections. It (Tripitikas) is called the Sutta Pitaka, the Abhidhamma Pitaka, and Vinaya Pitaka. The Sutta Pitaka means Basket of Discourse, Abhidhamma Pitaka means Basket of Special Doctrine.Vinaya Pitaka means Basket of Discipline. It includes the rules made for buddha community people. Three Baskets of Tripitaka is a traditional term used for various Buddhist scriptures. Sutta Pitaka is divided into \[5\]sections. It has approx. \[10,000\]sutras related to Buddha and his close associates. It is the postmortem of the teachings of Buddha. Vinaya Pitaka is divided into three books. It also deals with the \[1st\]Buddha council, held just after Buddha’s death. Abhidhammapitaka is divided into seven books. It comprises the philosophy and doctrine of Buddhism. These texts are those religious writings that are included in the Buddhist tradition. The first texts were passed orally by monastics. Later they were written down as manuscripts in many languages and many Buddhist canons.
So, the correct answer is Option D.

Note: Buddha's main writing is known as Pitakas. Tri means three i.e. the Vinaya Pitaka, Sutta Pitaka and the Abhidhamma Pitaka.