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]: Potassium helps maintain fluid regulation and normal pH. All ____ help normalize.\Question: Choose the right answer from options given a) three b) six c) two d) one
[EX A]: a

[EX Q]: Mares abort suddenly without signs of illness, and the fetus shows ____ signs of degenerative change.\Question: Choose the right answer from options given a) zero b) no c) seven d) ten
[EX A]: b

[EX Q]: Some sources place opium consumption in Teheran at ____ tons a day.\Question: Choose the right answer from options given a) five b) eight c) one d) three
[EX A]:
a