The correct answer is (b).
Gautama Buddha allowed the entry of women into the Buddhist Sangha at Vaisali. This was after he was persuaded by his aunt and foster mother, Mahapajapati Gotami, and his disciple Ananda.
Mahapajapati Gotami had been a devoted follower of the Buddha and had raised him after his mother died. She was eager to join the Sangha and practice the Buddha’s teachings, but she was initially refused permission because she was a woman.
Ananda, who was the Buddha’s attendant, also pleaded with the Buddha to allow women to join the Sangha. He argued that women were just as capable of practicing the Buddha’s teachings as men.
The Buddha eventually relented and allowed Mahapajapati Gotami and a group of other women to join the Sangha. This was a significant event in the history of Buddhism, as it allowed women to participate fully in the religious life.
The other options are incorrect. Sravasti, Rajagriha, and Kushinagar are all places where the Buddha lived and taught, but they are not the places where he allowed women to join the Sangha.