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: Copper is ____ times higher in dog liver than in human liver.\Question: Choose the right answer from options given a) three b) ten c) six d) one
Example Output: b

Example Input: Parapsychologists have ____ basic approaches to their subject matter.\Question: Choose the right answer from options given a) three b) two c) ten d) five
Example Output: b

Example Input: Crabs have ____ legs including the claws.\Question: Choose the right answer from options given a) five b) eight c) four d) ten
Example Output:
d