# $Cu+H_2\quad\underrightarrow {heat}\quad Cu+x$,$ZnO+y\quad\underrightarrow{heat} \quad Zn+H_2O$,$2AgCl+H_2\rightarrow z+w$.The $y$ is

$\begin{array}{1 1}(a)\;2H_2\\(b)\;2H_2O\\(c)\;H_2O\\(d)\;H_2\end{array}$

$ZnO+H_2\quad\underrightarrow{heat} \quad Zn+H_2O$
Hence y is $H_2$
Hence (d) is the correct answer.