Given:
Percentage of sulphur in the compound = 8%

To find:
Least molecular mass of the compound

Solution:
Assume that the compound has 100g mass.
Then, the mass of sulphur in the compound = 8g

Let the molecular formula of the compound be X.
Then, the molecular mass of X = m(X)

Now, we need to find the least value of m(X).

Since the percentage of sulphur in X is 8%, the mass of sulphur in X is 8% of m(X).
So, we can write:

Mass of sulphur in X = (8/100) × m(X)

Also, we know that the atomic mass of sulphur is 32 u.
So, the number of moles of sulphur in X is:

Number of moles of sulphur in X = (8g) / (32g/mol) = 0.25 mol

Let the number of moles of X be n.
Then, we can write:

n × m(X) = 100g

n × (32 + atomic mass of other atoms) = 100

n × (32 + m(X)/n - 32) = 100

m(X) = 68n

Substituting this in the equation above, we get:

68n² = 100

n² = 100/68 = 25/17

n = √(25/17)

Now, we need to find the least value of m(X), i.e., the value of m(X) when n is a whole number.

The smallest whole number greater than √(25/17) is 2.
So, we can assume that n = 2.

Substituting this in the equation above, we get:

m(X) = 68n = 136 u

Therefore, the least molecular mass of the compound is 136 u.

Answer: The correct option is B.

Molecular mass(let m)will be least when there's only one sulphur atom in a molecule .
m×8/100=32
m=400