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: Sexual reproduction involves ____ parents, one male and one female.\Question: Choose the right answer from options given a) zero b) two c) nine d) four
Example Output: b

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: Revolution is recommended for use in dogs and cats ____ weeks of age and older.\Question: Choose the right answer from options given a) zero b) seven c) two d) six
Example Output:
d