Option (a.), 'ailment', refers to an often-persistent bodily disorder or disease; a cause for complaining.
Therefore, option (a.) is wrong as its meaning isn't synonymous to it of the given word ‘handicap’.
Option (b.), ‘enhancement', refers to an improvement that produces something more agreeable
Therefore, option (b.) is wrong as its meaning isn't synonymous thereto of the given word ‘handicap’.
Option (c.), ‘advantage', refers to the standard of getting a superior or more favourable position.
Therefore, option (c.) is wrong as its meaning isn't synonymous to it of the given word ‘handicap’.
Option (d.), ‘burden', refers to a weight to be borne or conveyed.
Therefore, option (d.) is correct as its meaning is synonymous thereto of the given word ‘handicap’