The rules made for the Buddhist sangha were written down in a book called

The correct option is B. Vinaya Pitaka

The Vinaya Piṭaka is a Buddhist scripture, one of the three parts that make up the Tipiṭaka. The other two parts of the Tipiṭaka are the Sutta Piṭaka and the Abhidhamma Piṭaka.

The Vinaya records the Buddha's rules of discipline for monks and nuns. It also contains stories about the first Buddhist monks and nuns and how they lived.