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]: Some homeopathic remedies are so dilute, ____ molecules of the healing substance remain.\Question: Choose the right answer from options given a) ten b) three c) one d) no
[A]: d


[Q]: Plants grow up to ____ feet tall and spread to about three feet.\Question: Choose the right answer from options given a) three b) seven c) one d) no
[A]:
a