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]: Double price is based on two golfers sharing ____ room.\Question: Choose the right answer from options given a) one b) zero c) six d) nine
[A]: a


[Q]: Ankle sprains, muscle strains, and shin contusions are soccer s ____ most common injuries.\Question: Choose the right answer from options given a) three b) seven c) six d) zero
[A]:
a