The word, ‘deficit’ is an adjective which describes something being in shortage or inadequate or not enough. The word, ‘surplus’ is an adjective which is used to describe something in excess or abundance or more than enough. It may be observed that the two words convey opposite meanings. Hence, 'surplus' is the antonym of 'deficit' and option D is the correct answer.
The word ‘profit’ is a noun which means ‘financial gain’. It refers to the difference between the amount earned and the amount spent. The word, ‘bonus’ is a noun which means ‘extra benefit, mostly monetary’. The word, ‘benefit’ is a noun means ‘advantage or profit gained from something’.
As all the above words 'profit', 'bonus' and 'benefit' are not adjectives and do not convey the same meaning as 'excess' or 'abundance', options A, B and C are incorrect.