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').

Brachiopods are superficially similar to bivalves, both having ____ shells.\Question: Choose the right answer from options given a) two b) eight c) seven d) one
a

Prairie voles look like rodents with small rounded bodies, ____ short legs and a short tail.\Question: Choose the right answer from options given a) two b) nine c) four d) zero
c

Statistics show that ____ out of every four people has a mental illness.\Question: Choose the right answer from options given a) seven b) one c) eight d) five

b