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').

Q: Many aneurysms have ____ symptoms until they burst.\Question: Choose the right answer from options given a) no b) five c) six d) seven

A: a
****
Q: Intensity is defined as the average of the extreme anomalies during ____ consecutive months.\Question: Choose the right answer from options given a) ten b) three c) two d) five

A: b
****
Q: Every oxygen links to one silica tetrahedron and ____ ferromagnesian octahedra.\Question: Choose the right answer from options given a) three b) zero c) ten d) one

A:
a
****