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: Toucanets encompass ____ genera.\Question: Choose the right answer from options given a) seven b) six c) two d) one
Example Output: c

Example Input: Routers are basically systems, which connect ____ networks together.\Question: Choose the right answer from options given a) three b) two c) nine d) six
Example Output: b

Example Input: Lemon sharks are usually ____ to ten feet long.\Question: Choose the right answer from options given a) eight b) ten c) zero d) four
Example Output:
a