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]: Rock cavies become sexually mature when they are about one to ____ months old.\Question: Choose the right answer from options given a) one b) four c) three d) seven
[EX A]: c

[EX Q]: Antimony trioxide is found in ____ minerals, valentinite and senarmontite.\Question: Choose the right answer from options given a) five b) nine c) eight d) two
[EX A]:
d