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: Some homeopathic remedies are so dilute, ____ molecules of the healing substance remain.\Question: Choose the right answer from options given a) ten b) three c) one d) no
Example Output: d

Example Input: Electrolytic capacitors have a finite lifetime, usually about ____ years.\Question: Choose the right answer from options given a) zero b) ten c) four d) eight
Example Output: b

Example Input: Insects have ____ lungs or centralized respiratory system.\Question: Choose the right answer from options given a) nine b) no c) two d) ten
Example Output:
b