Option 1, Choudhary Charan Singh, was not a member of the Rajya Sabha at the time of his appointment as Prime Minister. Option 2, Mrs. Indira Gandhi, was a member of the Rajya Sabha at the time of her appointment as Prime Minister. Option 3, Lal Bahadur Shastri, was not a member of the Rajya Sabha at any time during his tenure as Prime Minister. Option 4, P.V. Narasimha Rao, was not a member of the Rajya Sabha at the time of his appointment as Prime Minister. Therefore, the correct answer is option 2, Mrs. Indira Gandhi. She served as a member of the Rajya Sabha from 1964 to 1967 and was appointed as Prime Minister in 1966.