You are given a science question (hard-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.

Which best demonstrates that waves transfer energy?  
 (A) a bell ringing in a tower (B) a leaf falling from a tree (C) a ball rolling down a hill (D) a flag moving in the wind
A

Robert put two drops of an indicator into vinegar, and the color turned red. He then added drops of ammonia solution until the color disappeared. What process occurred?  
 (A) rusting (B) melting (C) evaporation (D) neutralization
D

The waves that are produced by a person's voice are similar to the waves produced by an earthquake because both are  
 (A) caused by physical vibrations. (B) moved by the force of gravity. (C) types of electromagnetic waves. (D) of the same frequency.

A

