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]: Mammals have only ____ sets of teeth.\Question: Choose the right answer from options given a) six b) five c) seven d) two
[A]: d


[Q]: Sexual reproduction involves ____ individual organisms.\Question: Choose the right answer from options given a) six b) no c) two d) nine
[A]: c


[Q]: All comatulids apparently develop ____ initial, radially-oriented cirri.\Question: Choose the right answer from options given a) four b) two c) zero d) five
[A]:
d