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: Ultrasonic liposuction fits into ____ categories.\Question: Choose the right answer from options given a) two b) seven c) nine d) one
Example Output: a

Example Input: Most aphthous ulcers heal in one to ____ weeks.\Question: Choose the right answer from options given a) two b) eight c) one d) seven
Example Output: a

Example Input: Genetic mapping divides the chromosomes in ____ bands.\Question: Choose the right answer from options given a) ten b) two c) four d) nine
Example Output:
b