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: Poisons come in ____ different forms .\Question: Choose the right answer from options given a) four b) no c) five d) ten
Example Output: a

Example Input: Many animals use two or ____ forest structure types.\Question: Choose the right answer from options given a) eight b) zero c) two d) three
Example Output: d

Example Input: Cellular respiration occurs in ____ parts.\Question: Choose the right answer from options given a) one b) seven c) eight d) three
Example Output:
d