To determine in which temple Ramanuja taught, we need to understand the historical background of Ramanuja and his teachings.

Ramanuja was a prominent Hindu philosopher and theologian who lived in the 11th and 12th centuries. He is considered one of the most important exponents of the Sri Vaishnavism tradition, which is a sect of Hinduism that worships the deity Vishnu.

Ramanuja is known for his teachings and commentaries on the Vedas, Upanishads, and the Bhagavad Gita. He traveled extensively and imparted his teachings in various places, particularly in South India.

Among the given options, the temple where Ramanuja taught is:

B. Sri Rangam

Sri Rangam is a renowned temple dedicated to Lord Ranganatha, a form of Lord Vishnu, located in Tamil Nadu, South India. It is one of the most important and largest functioning temples in the world. Ramanuja spent a significant amount of time at Sri Rangam, where he taught and disseminated his teachings on Sri Vaishnavism.

Therefore, the correct answer is B. Sri Rangam.