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').

[EX Q]: Birds have ____ eyes.\Question: Choose the right answer from options given a) eight b) five c) nine d) two
[EX A]: d

[EX 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
[EX A]: b

[EX Q]: Cows can manufacture proteins ____ times more efficiently than laboratory cell cultures.\Question: Choose the right answer from options given a) six b) eight c) five d) nine
[EX A]:
c