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: Poles CAN occur at ____ frequency.\Question: Choose the right answer from options given a) six b) four c) zero d) eight

A: c
****
Q: Baby elephants are usually dependent on mother s milk for at least ____ years.\Question: Choose the right answer from options given a) six b) three c) two d) seven

A: b
****
Q: Xenon is an odourless, colourless, chemically inert gas with ____ stable isotopes.\Question: Choose the right answer from options given a) zero b) no c) nine d) one

A:
c
****