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').

Calves remain hidden for much of the time, and are weaned by ____ months of age.\Question: Choose the right answer from options given a) six b) three c) eight d) one
b

Selenium is ____ times more poisonous than arsenic.\Question: Choose the right answer from options given a) one b) five c) eight d) two
b

Covariance is a measure of the distributions of ____ variables.\Question: Choose the right answer from options given a) seven b) no c) two d) four

c