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: Most resistors have three coloured bands close together at one end and ____ single band at the other.\Question: Choose the right answer from options given a) two b) one c) ten d) five
Example Output: b

Example Input: Females can only have four babies at ____ time.\Question: Choose the right answer from options given a) no b) one c) nine d) three
Example Output: b

Example Input: Full immunity occurs about ____ weeks after injection and lasts for about five months.\Question: Choose the right answer from options given a) six b) four c) nine d) eight
Example Output:
b