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: 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

A: a
****
Q: Females can only have four babies at ____ time.\Question: Choose the right answer from options given a) no b) one c) nine d) three

A: b
****
Q: Social science comes in ____ forms, which work together.\Question: Choose the right answer from options given a) no b) two c) one d) three

A:
b
****