Option b is the correct answer. The entry of women as bhikkhunis (nuns) into the Buddhist Sangha was allowed by Gautama Buddha at Vaishali, a city in the Indian state of Bihar. The Buddha let women become Bhikshuni and join the sangha in Vaishali because Anand, his student, persuaded him for it. Mahaprajapati Gautami was the first woman to join the sangha.