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 spiders have ____ eyes and eight legs.\Question: Choose the right answer from options given a) eight b) five c) no d) three
[EX A]: a

[EX Q]: Food chains consist of ____ trophic levels.\Question: Choose the right answer from options given a) ten b) three c) one d) four
[EX A]: d

[EX Q]: Snails can penetrate a shell as thick as ____ millimeters.\Question: Choose the right answer from options given a) zero b) four c) eight d) five
[EX A]:
d