$$ \text { The IUPAC name of the following compound is } $$

An alkyne has the molecular formula $\mathrm{C}_6 \mathrm{H}_{10}$. The number of 1 -alkyne isomers (excluding stereoisomers) possible for it is

A metal crystallises in two cubic phases, fcc and bcc with edge lengths $3.5 \mathop {\rm{A}}\limits^{\rm{o}}$ and $3 \mathop {\rm{A}}\limits^{\rm{o}}$ respectively. The ratio of densities of fcc and bcc is approximately

Observe the following data given in the table ( $K_H=$ Henry's law constant)

$$ \begin{aligned} &\begin{array}{ccccc} \hline \text { Gas } & \mathrm{CO}_2 & \mathrm{Ar} & \mathrm{HCHO} & \mathrm{CH}_4 \\ \hline\left(\boldsymbol{K}_{\mathrm{H}} \text { bar at } \mathbf{2 9 8 ~ K}\right) & 1.67 & 40.3 & 1.83 \times 10^{-5} & 0.413 \\ \hline \end{array}\\ &\text { The correct order of their solubility in water is } \end{aligned} $$