Producer gas is a mixture of

Which of the following non-metal elements has half the atomicity of sulfur?

Which property of $CO_2$ makes it biologically and geo-chemically important?

In the dimer of phosphorus pentaoxide $(P_4O_{10})$,what is the correct order of the number of $P-O-P$,$P=O$,and $P-P$ bonds?

The correct statements with respect to halides of group $14$ elements are:
$I$. Both $CCl_4$ and $SiCl_4$ undergo hydrolysis
$II$. $GeX_4$ is more stable than $GeX_2$
$III$. $PbX_4$ is less stable than $PbX_2$
$IV$. Stability of dihalides decreases down the group.

Which one of the following elements reacts with steam?