In which of the following texts were Buddha’s teachings compiled ?

Sutta Pitaka is one of the three main divisions of the Tripitaka (Pali Canon), which contains the teachings (discourses) of Gautama Buddha.

It includes sermons, dialogues, and stories related to ethical and philosophical teachings of Buddhism.

Written in Pali, it is a key source for Theravāda Buddhism.

Let's look at the other options:
(A) Uttaradhyayana Sutta – A Jain text, containing teachings of Mahavira.

(C) Kalpasutra – Also a Jain text, mainly biographical, detailing lives of Tirthankaras.

(D) Rigveda – A Vedic text, part of Hindu literature, composed much earlier and unrelated to Buddhism.

So, the Sutta Pitaka is the correct answer for Buddha’s compiled teachings.