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: Motor neurons are divided into ____ groups.\Question: Choose the right answer from options given a) two b) six c) seven d) eight
Example Output: a

Example Input: Quarks also come in ____ 'colours', terms for a property a little like electrical charge.\Question: Choose the right answer from options given a) three b) nine c) six d) no
Example Output: a

Example Input: Ostriches come in at least ____ breeds.\Question: Choose the right answer from options given a) nine b) ten c) eight d) two
Example Output:
d