The strongest reducing agent and strongest oxidising agent are respectively

A reducing agent is the one that it itself oxidized as it loses electrons whereas a oxidizing agent is the one that it itself reduced as it gains electrons.

Cs has high metallic character and easily looses electrons, thereby it is considered as a strong reducing agent. 

Fluorine is an element that has high electronegativity and the highest reduction potential so more able to lose electrons, thus it is the strongest oxidizing agent.

Hence, option(c) is correct.