A metal $X$ does not react with cold water but reacts with hot water to form its hydroxide.Metal $X$ is more reactive than iron but less reactive than sodium.
Metal $X$ is:

The correct option is B Magnesium
$Zn$ reacts with steam only and it does not react with hot water or cold water.
$Mg$ reacts with hot water and steam but not with cold water and $Mg$ is more reactive than $Fe$ and less reactive than sodium.
$Ca$ reacts with cold water and $Al$ does not react with hot water.