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]: Black widows mature in ____ to four months.\Question: Choose the right answer from options given a) two b) seven c) eight d) zero
[EX A]: a

[EX Q]: Female cats can go into heat for the first time as early as ____ months of age.\Question: Choose the right answer from options given a) four b) zero c) five d) eight
[EX A]: c

[EX Q]: Lenses have ____ main shapes.\Question: Choose the right answer from options given a) three b) one c) four d) two
[EX A]:
a