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]: Heme is made of ____ pyrrole groups united to form a porphyrin ring.\Question: Choose the right answer from options given a) five b) four c) eight d) six
[A]: b


[Q]: Pairs encodes all sets of objects with ____ components.\Question: Choose the right answer from options given a) ten b) five c) two d) no
[A]: c


[Q]: Pineapples take between one and ____ years to produce fruit.\Question: Choose the right answer from options given a) no b) two c) nine d) three
[A]:
d