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: ATMs are expensive machines with an average useful life of ____ to fifteen years.\Question: Choose the right answer from options given a) nine b) eight c) ten d) two
Example Output: c

Example Input: Tropical trees can be rampant growers, and can outgrow a wiring in as little as ____ days' time.\Question: Choose the right answer from options given a) four b) eight c) six d) ten
Example Output: d

Example Input: Gold is only pure when there are ____ alloys present.\Question: Choose the right answer from options given a) four b) two c) zero d) no
Example Output:
d