The correct answer is (C) A platform, a pulpit; any stage for public speaking. Also, a beaklike prow of a ship, especially an ancient war galley; a stiff beaklike part for ramming an enemy ship.

Rostrum comes from Latin rostrum (bill, beak)

Examples of use:

• The winning speech was presented to the entire school from the rostrum.
• The political candidate stepped up to the rostrum to deliver his address. duet.