As we can say that ,
forgiving is opposite word of Vengeful .

Correct Option: A

As we can say that ,
Vengeful is full of vengeance, i.e., anger and revenge; forgiving will be opposite to taking revenge; Vindictive is to attack and Vicious is something evil.
Hence , forgiving is opposite word of Vengeful .

As we can say that ,
Unmanageable is opposite word of Tractable

Correct Option: C

As we can say that ,
Tractable is something that can be managed easily, i.e., manageable.
From above it is clear that Unmanageable is opposite word of Tractable .

As we can say that ,
Obese is antonym word of Cadaverous .

Correct Option: B

As we can say that ,
Cadaverous is very slim or thin, obese is very fat, lucid means clearly expressed, inquisitive is to be very curious, and Skilful is someone who shows great skill.
Thus , Obese is antonym word of Cadaverous .

As we can say that ,
Barren is antonym word of Prolific

Correct Option: A

As we can say that ,
Prolific means fecund or very productive, Barren means unproductive, reckless is wildly impulsive, profound is something with much depth (of meaning).
Therefore , Barren is antonym word of Prolific .

As per the given above word , we can say that
Unmanageable is antonym word of Docile .

Correct Option: A

As per the given above word , we can say that
Docile means submissive and therefore can be controlled very easily, unmanageable is someone or something that cannot be controlled or managed easily.
From above it is clear that Unmanageable is antonym word of Docile .