A. Cat : Mouse

B. Curd : Bacteria

C. Fruit : Rubber

D. Sun : Moon 

 Justification:

Leather and milk are both obtained from animals.
Similarly, fruit and rubber are both obtained from trees.

A. Gun : Cartridge

B. Rice : Husk

C. Milk : Cream

D. Serial : Episode

 Justification: Second is a part of the first.

A. Vaccination : Immunity

B. Sculptor : Statue

C. Degree : Graduate

D. Summer : Rain 

 Justification: First is followed by the second.

A. Man : Energy

B. Machine : Oil

C. Current : Electricity

D. River : Water

Justification: First needs the second to work.

A. Disease : Medicine

B. Famous : Notorious

C. Food : Energy

D. Treaty : Peace

A. Hockey : Stick

B. Cricket : Bat

C. Skating : Rink

D. Football : Goal

  Justification:

Badminton is played in a court.
Similarly, skating is done in a rink.

A. Cockroach : Insect

B. Bedsheet : Bed

C. Pillow : Cushion

D. Mat : Floor

 Justification:

 The second denotes the class to which the first belongs.

A. Fish : Water

B. Whale : Fish

C. Lizard : Insect

D. Man : Homosapiens

 Justification:

The second denotes the class to which the first belongs.

A. Dirty : Filthy

B. Disorderly : Unfaithful

C. Raise : Commensurate

D. Promoted : Excellence

 Justification:

 The second is of higher intensity than the first.