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: Organisms have ____ forms of nucleic acid.\Question: Choose the right answer from options given a) four b) three c) two d) one
Example Output: c

Example Input: Mechanical stability comes from having fused quartz, in ____ gravity, cold.\Question: Choose the right answer from options given a) five b) zero c) six d) two
Example Output: b

Example Input: Rice is categorized by size into ____ broad groups - long, medium or short grain.\Question: Choose the right answer from options given a) seven b) three c) six d) nine
Example Output:
b