Antonym of the given word

abet 

The path traced by planet is called Orbit. Similarly, the path traced by projectile is called Trajectory.

Hence, Planet : Orbit : : Projectile : Trajectory.

Here the given words, sullen and moody are synonyms to each other which means that gloomy, resentful. Similarly, repetitious and monotonous are synonyms to each other which means dull, tedious.

Hence, Sullen : moody :: monotonous : repetitious.

Given 2 is to 55

2 + 3 = 5 

5 x 11 = 55

Similarly, 6

6 + 3 = 9

9 x 11 = 99

Hence, 2 is to 55 as 6 is to 99.

A rowboat can be put into motion by using oar. Similaarly, a skateboard can be put into motion by using foot.

The other options like walk and running are not objects to be in motion. And loafers are something worn on foot.

Hence, Oar : Rowboat :: Foot : Skateboard.

We know that, a folder holds documents in the same way an envelope holds letters.

Hence, Folder : Document :: Envelope : Letter.

As Tennis is a kind of Sport, similarly, Chemistry is a kind of science.

Hence, Tennis : Sport :: Chemistry : Science.

The given words are related in such a manner that, for exercise we go to gym. Simmilarly, for eating we go to restaurent.

Hence, Exercise : Gym :: Eating : Restaurent.

A book is consists of various chapters, so as the Organization consists of various departments. Therefore if Book is to chapter so organization is to department.

Hence, Book : Chapter :: Organisation : Department.