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').
--------
Question: Most people require roughly seven to ____ hours of sleep a night to stay alert through the day.\Question: Choose the right answer from options given a) eight b) ten c) one d) five

Answer: a


Question: Natural tellurium consists of ____ isotopes.\Question: Choose the right answer from options given a) six b) seven c) eight d) one

Answer: c


Question: Babies are breast-fed until about ____ years of age.\Question: Choose the right answer from options given a) four b) nine c) eight d) two

Answer:
d