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').

[EX Q]: Color codes are ____ digit combinations of letters and numbers that correspond to a specific color.\Question: Choose the right answer from options given a) six b) eight c) seven d) one
[EX A]: a

[EX Q]: Collars come in ____ shapes.\Question: Choose the right answer from options given a) six b) two c) four d) zero
[EX A]: b

[EX Q]: Some desmids contain ____ chloroplasts per cell.\Question: Choose the right answer from options given a) two b) zero c) four d) one
[EX A]:
a