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: Most gerbils live three to ____ years and have few health problems.\Question: Choose the right answer from options given a) three b) four c) seven d) zero

A: b
****
Q: Most bacteria have one or ____ circular chromosomes.\Question: Choose the right answer from options given a) ten b) eight c) six d) two

A: d
****
Q: Most eels have ____ scales and are protected by a layer of slippery mucus.\Question: Choose the right answer from options given a) three b) no c) ten d) eight

A:
b
****