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').

Q: Electrolytic capacitors have a useful life of about ____ years.\Question: Choose the right answer from options given a) ten b) eight c) zero d) seven

A: a
****
Q: Infants usually die of pneumonia or other infections before reaching ____ years of age.\Question: Choose the right answer from options given a) nine b) four c) zero d) eight

A: b
****
Q: Cancer is the number ____ killer behind heart disease.\Question: Choose the right answer from options given a) eight b) zero c) two d) nine

A:
c
****