You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

[Q]: Which of the following is most likely to disrupt the natural balance in an ecosystem?  
 (A) introduction of a non-native species (B) reduced daylight hours during winter (C) preventing the cutting of trees in forests (D) riverbank erosion resulting from springtime flooding
[A]: A


[Q]: As water cools to a temperature of zero degrees Celsius and forms ice, water molecules tend to  
 (A) move farther apart. (B) vibrate rapidly. (C) flow more randomly. (D) gradually expand.
[A]: A


[Q]: Elizabeth uses a specific type of whistle to call her dogs. The noise made by the whistle is heard by the dogs but cannot be heard by the human ear. Which statement best describes why humans cannot hear the sound made by the whistle?  
 (A) The speed of the sound is too fast. (B) The amplitude of the sound is too low. (C) The frequency of the sound is too high. (D) The wavelength of the sound is too long.
[A]:
C