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: Cows have four stomachs, and the first ____ yield merchantable tripe.\Question: Choose the right answer from options given a) two b) five c) zero d) three

Answer: d


Question: All birds have ____ legs with four toes each.\Question: Choose the right answer from options given a) zero b) one c) three d) two

Answer: d


Question: Melanocytes are dendritic and are distributed roughly ____ per six basal cells.\Question: Choose the right answer from options given a) one b) no c) six d) ten

Answer:
a