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').
--------
Question: 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

Answer: b


Question: Cows breed at ____ years, bulls at four.\Question: Choose the right answer from options given a) two b) three c) seven d) one

Answer: b


Question: Plants grow in ____ ways, cell division and cell expansion.\Question: Choose the right answer from options given a) seven b) ten c) two d) six

Answer:
c