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]: Sexual reproduction involves ____ parents, one male and one female.\Question: Choose the right answer from options given a) zero b) two c) nine d) four
[A]: b


[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]: High stress has the highest pitch, about ____ notes above a vowel without a stress mark.\Question: Choose the right answer from options given a) four b) five c) no d) two
[A]:
a