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').

Worker bees have ____ pairs of wax glands on the underside of their abdomens.\Question: Choose the right answer from options given a) no b) two c) nine d) four
d

Nodes are points in space that have ____ probability for locating an electron there.\Question: Choose the right answer from options given a) no b) six c) zero d) three
c

Sexual maturity is reached at ____ years of age, and most fish die by age six.\Question: Choose the right answer from options given a) no b) seven c) six d) three

d