(Stallion : Colt) , (Horse : More) , (Dog : Bitch) , (Drake : Duck) , (Drone : Bee)
Option:
Justification: In all other pairs, second is the female of the first.

(Stallion : Colt) , (Horse : More) , (Dog : Bitch) , (Drake : Duck) , (Drone : Bee)
Justification: In all other pairs, second is the female of the first.