The correct option is B Superior
An antonym is a word that has an opposite meaning of another word.
The given word 'inferior' refers to someone who is low in rank or something that is low in quality, for example, 'This bag is of inferior quality.'
From the options, 'superior' means the opposite: it refers to someone who has a higher rank or something that has a higher quality, for example, 'The quality of the bags in this boutique is superior to the quality of those sold in the market.' Hence 'superior' is the antonym of 'inferior' and option B is correct.
'Secondary' means 'less important than', it is similar to 'inferior', hence option A is incorrect.
Similarly, 'subsidiary' means 'of lesser importance', hence C is incorrect.
'Minor' is also synonymous with 'inferior'. It means lesser in importance or significance. Hence D is incorrect.