Who were the 'theris' in Buddhism?

Respected women who had attained liberation.

The correct answer is Option 4 - Respected women who had attained liberation.

Many women who entered the sangha became teachers of dhamma and went on to become theris, or respected women who had attained liberation.

Initially, only men were allowed into the sangha, but later women also came to be admitted. According to Buddhist texts, this was made possible through the mediation of Ananda, one of the Buddha’s dearest disciples, who persuaded him to allow women into the sangha. The Buddha’s foster mother, Mahapajapati Gotami was the first woman to be ordained as a bhikkhuni. Many women who entered the sangha became teachers of dhamma and went on to become theris, or respected women who had attained liberation.