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').
--------
Question: Dunes are of ____ types - linear and parabolic.\Question: Choose the right answer from options given a) three b) four c) ten d) two

Answer: d


Question: Mosquitoes spend one to ____ days in the pupae stage.\Question: Choose the right answer from options given a) zero b) two c) five d) three

Answer: b


Question: All vertebrates produce interferons, and all appear to produce the ____ major classes.\Question: Choose the right answer from options given a) seven b) ten c) five d) three

Answer:
d