The correct option is A
1 only
Explanation:
Statement 1 is correct.
When a vacancy occurs in the office of the President due to his resignation, impeachment, death or otherwise, he acts as President. Further, when the sitting President is unable to discharge his functions due to absence, illness or any other cause, the Vice-President discharges his functions until the President resumes his office.
However, the Speaker of Lok Sabha cannot act as the President during his office term.
Statement 2 is incorrect.
Unlike the Speaker who is a member of the House, the Chairman is not a member of the House.
Statement 3 is incorrect.
There will be no elections to the office of Chairman of Rajya Sabha. The Vice president is the ex-officio chairman of Rajya Sabha. On the other hand, the Speaker is elected by the Lok Sabha from amongst its members as soon as may be, after its first sitting.