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: Studies show that childhood obesity is epidemic and that ____ in five children is overweight.\Question: Choose the right answer from options given a) one b) two c) nine d) ten
Example Output: a

Example Input: Nymphs feed and mature through five instars in about ____ to eight weeks.\Question: Choose the right answer from options given a) six b) five c) seven d) zero
Example Output: a

Example Input: Minerals can also have two, three, four or ____ cleavage planes.\Question: Choose the right answer from options given a) eight b) five c) no d) six
Example Output:
d