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: Background radiation comes from ____ sources.\Question: Choose the right answer from options given a) zero b) three c) four d) no

Answer: b


Question: Angiosperms inhabit all ____ continents, as well as the oceans.\Question: Choose the right answer from options given a) five b) seven c) three d) zero

Answer: b


Question: Euthanasia rests on ____ prongs.\Question: Choose the right answer from options given a) six b) two c) ten d) eight

Answer:
b