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: Reservoirs cover an area of the planet ____ times the size of Britain.\Question: Choose the right answer from options given a) two b) eight c) three d) six
Example Output: d

Example Input: Coccidiosis usually occurs from ____ weeks of age.\Question: Choose the right answer from options given a) zero b) no c) three d) eight
Example Output: c

Example Input: Plants synthesize ____ types of polysaccharides, starch and cellulose.\Question: Choose the right answer from options given a) zero b) one c) three d) two
Example Output:
d