What is X in the following sequence of reactions? $$X\quad\underrightarrow{Na}\quad Y\quad\underrightarrow{NaOH/CaO}\quad CH_4$$

Question

$\begin{array}{1 1}(a)\;\text{Methanoic acid}\\ (b)\;\text{Ethanoic acid}\\(c)\;\text{Propane}\\(d)\;\text{Methane}\end{array}$