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').

[EX Q]: Most internal parasites are specific to one or ____ species.\Question: Choose the right answer from options given a) seven b) three c) two d) five
[EX A]: c

[EX Q]: Most bioluminescence is blue for ____ reasons.\Question: Choose the right answer from options given a) seven b) two c) four d) zero
[EX A]: b

[EX Q]: Spatial filters have ____ functions.\Question: Choose the right answer from options given a) no b) two c) six d) three
[EX A]:
b