Step 1: Distinguish Head of State from Head of Government.
In India's parliamentary system, these two roles are held by different people.
Step 2: Apply Article 52.
Article 52 of the Indian Constitution states that there shall be a President of India, who is the constitutional Head of State. The President is the supreme executive authority in form, though real executive power lies with the Council of Ministers.
Step 3: Eliminate wrong options.
The Prime Minister is the Head of Government. The Speaker and Chairman of Rajya Sabha are presiding officers, not Heads of State.
\[ \boxed{\text{the President of India}} \]