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').

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
c

Lions have ____ distinct vocalizations including roars, grunts and growls.\Question: Choose the right answer from options given a) eight b) six c) four d) nine
d

Pipes can vibration in ____ orthogonal directions just like a machine.\Question: Choose the right answer from options given a) nine b) three c) six d) ten

b