The correct choice is (c) Polyclar
To explain I would say: Polyclar is an artificial clarifying agent which is used to make the beer appear bright and clean., rather than cloudy appearance. Isinglass (obtained from swimbladders of fish), Irish moss (a seaweed), and kappa carrageenan (obtained from seaweed Kappaphycus cottonii) are the examples of natural clarifying agents.