Pick out the antonym(s) for 'victor'
‘Victor’ means ‘a person who defeats an opponent’ and ‘loser’ means ‘one who gets defeated’. So option B is the right answer.
‘Winner’ means ‘the one who wins’. It is a synonym of ‘victor’. Thus, option A is incorrect.
‘Rival’ means ‘opponent/competitor’. It refers to the competitor and not the outcome of the competition. So, option C is incorrect.
‘Master’ means ‘teacher’. It is not an appropriate antonym for victor. So, option D is incorrect.