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: Normal cells have ____ copies of each chromosome.\Question: Choose the right answer from options given a) two b) five c) eight d) no

A: a
****
Q: China has about ____ in four of all smokers in the world.\Question: Choose the right answer from options given a) one b) seven c) ten d) six

A: a
****
Q: Ponies lose their baby teeth by ____ years, then their big teeth gradually wear down.\Question: Choose the right answer from options given a) six b) nine c) five d) seven

A:
c
****