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:
Human malaria is caused by ____ species of Plasmodium . .\Question: Choose the right answer from options given a) six b) ten c) seven d) four

Ex Output:
d


Ex Input:
Brain death occurs in just four to ____ minutes unless the heart rhythm is restored.\Question: Choose the right answer from options given a) ten b) three c) six d) nine

Ex Output:
c


Ex Input:
Medical drugs can only kill one or ____ parasites each.\Question: Choose the right answer from options given a) two b) eight c) ten d) no

Ex Output:

a