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]: Ascidian tunicates come in ____ main forms.\Question: Choose the right answer from options given a) three b) zero c) four d) eight
[A]: a


[Q]: Takins can even balance on their hind hooves to nibble on vegetation ____ feet above ground.\Question: Choose the right answer from options given a) two b) no c) nine d) eight
[A]: d


[Q]: Antibodies exist as ____ or more copies of a Y-shaped unit, composed of four polypeptide chains.\Question: Choose the right answer from options given a) zero b) six c) one d) nine
[A]:
c