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').

Example Input: Nematodes occur in ____ general forms.\Question: Choose the right answer from options given a) nine b) two c) seven d) ten
Example Output: b

Example Input: Big bluestem grows up to ____ feet tall.\Question: Choose the right answer from options given a) seven b) no c) nine d) eight
Example Output: c

Example Input: Baryons contain three quarks while mesons contain only ____ quarks.\Question: Choose the right answer from options given a) two b) eight c) four d) seven
Example Output:
a