Given a sentence with a missing word, pick the answer option that best fills out the missing word in the sentence. Indicate each answer with its index ('a', 'b', 'c', 'd').

Ex Input:
Dogs are pack animals, and ____ dogs is the minimum number for proper socialization.\Question: Choose the right answer from options given a) four b) five c) no d) zero

Ex Output:
b


Ex Input:
Hydra has ____ distinct methods of reproduction, asexual and sexual.\Question: Choose the right answer from options given a) two b) zero c) no d) ten

Ex Output:
a


Ex Input:
Pyrimidines contain ____ ring and purines contain two rings.\Question: Choose the right answer from options given a) ten b) eight c) no d) one

Ex Output:

d