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: 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

A: d
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Q: Human malaria is caused by ____ species of Plasmodium . .\Question: Choose the right answer from options given a) six b) ten c) seven d) four

A: d
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Q: Water is the only known substance that commonly exists in all ____ phases at once.\Question: Choose the right answer from options given a) three b) seven c) five d) no

A:
a
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