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').
--------
Question: Tetrapods are animals that have ____ legs or leg-like appendages.\Question: Choose the right answer from options given a) four b) one c) ten d) six

Answer: a


Question: Banks hold ____ excess reserves and the public holds no currency.\Question: Choose the right answer from options given a) two b) seven c) ten d) no

Answer: d


Question: Digital bandwidth enables signal to be condensed as a ____ to one ratio.\Question: Choose the right answer from options given a) one b) two c) zero d) five

Answer:
d