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').

Nematodes occur in ____ general forms.\Question: Choose the right answer from options given a) nine b) two c) seven d) ten
b

Many soils have ____ major layers or horizons, top soil, subsoil and parent material.\Question: Choose the right answer from options given a) one b) two c) seven d) three
d

Rainbow trout breed every ____ to five years.\Question: Choose the right answer from options given a) zero b) five c) three d) four

c