The substance used as froth stabilisers in forth-floatation process is

In the froth-flotation process sulphide ores are concentrated by preferentially making the ore particles hydrophobic so that they can be carried to the surface along with the froth, while the gangue remains wetted by water and sinks.

Three different types of reagents are added to the slurry:

1. Collectors - These increase the non-wettability (hydrophobic character) of the mineral surface. A very common collector is potassium ethyl xanthate.
2. Frothers - These generate a persistent foam (froth) so that the hydrophobic ore particles can rise with the bubbles. Pine oil is a typical frother.
3. Froth stabilisers - These keep the formed froth stable for a longer time, preventing the bubbles from bursting prematurely.

Typical froth stabilisers are aromatic amines and cresols. Aniline, $$C_6H_5NH_2$$, is an aromatic amine and is therefore employed to stabilise the froth.

Hence, the substance used as a froth stabiliser in the froth-flotation process is
Option B which is: Aniline