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]: Metabolism have ____ stages-catabolism and anabolism.\Question: Choose the right answer from options given a) nine b) two c) five d) three
[A]: b


[Q]: Aridity presents ____ main obstacles to solitary behavior.\Question: Choose the right answer from options given a) no b) three c) two d) five
[A]: c


[Q]: Intermodal transportation minimizes transportation costs in ____ ways.\Question: Choose the right answer from options given a) no b) three c) two d) one
[A]:
c