Mammootty, the renowned Malayalam actor, has won the National Film Award for Best Actor three times: for 'Mathilukal' (1989), 'Ponthan Mada' (1993), and 'Dr. Babasaheb Ambedkar' (2000). This makes option C (3) the correct answer.
Malayalam actor Mammootty has won the National Film Award for Best Actor three times — for Mathilukal/Vidheyan (1989), Ponthan Mada (1993), and Vanaprastham (1999) — making him one of Indian cinema's most decorated performers in that category.