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 properties best describes a material's ability to resist scratching?  
 (A) weight (B) flexibility (C) length (D) hardness
[A]: D


[Q]: Some events on Earth happen instantly while others take thousands of years to occur. Which process takes the longest time to complete?  
 (A) rivers rising due to storms and floods (B) evaporation of water from the leaves of a plant (C) weathering of a rock to form small rocks and sand (D) movement of small pieces of rock by flowing water
[A]: C


[Q]: The surface of Earth is covered by a relatively thin layer of water called the  
 (A) crust (B) mantle (C) hydrosphere (D) atmosphere
[A]:
C