A compound possesses 8% sulphur by mass.The least molecular mass is

$\begin{array}{1 1}(a)\;200&(b)\;400\\(c)\;155& (d)\;355\end{array}$

The compound has sulphur=8%
$\therefore$ 8g of S is present in 100g
$\therefore$ 32g of S is present in $\large\frac{100}{8}$$\times 32=400g$
[Least molecular mass means that at least one atom of sulphur should be present in molecule]
Hence (b) is the correct answer.