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]: Diatoms look like ____ shells that fit together.\Question: Choose the right answer from options given a) zero b) one c) two d) seven
[A]: c

[Q]: Most linguists organize the African languages into ____ major language families.\Question: Choose the right answer from options given a) three b) four c) eight d) no
[A]: b

[Q]: Roots provide ____ important functions for the plant.\Question: Choose the right answer from options given a) zero b) two c) four d) seven
[A]:
b