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: Rheumatic fever begins one to ____ weeks after an untreated streptococcal infection.\Question: Choose the right answer from options given a) six b) ten c) two d) zero

A: a
****
Q: Corms are undifferentiated, uniform, and contain ____ rings when cut apart.\Question: Choose the right answer from options given a) no b) three c) one d) zero

A: a
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Q: Adult birds moult at least once a year, although many moult twice and a few ____ times each year.\Question: Choose the right answer from options given a) four b) zero c) three d) ten

A:
c
****