TASK DEFINITION: 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.
PROBLEM: Growth and activities of organisms can speed up the chemical weathering of rocks. Which organisms naturally cause most of the chemical weathering of rocks?  
 (A) small mammals (B) plant seedlings (C) mosses (D) insects

SOLUTION: C

PROBLEM: Leopard's opening chant suggests that he is  
 (A) unhappy. (B) confused. (C) confident. (D) generous.

SOLUTION: C

PROBLEM: Desalination removes salt from water. Removing salt from water can be risky because the process is expensive and slow. Sometimes the technology does not work. A beach community's surface and ground water was decreasing. The community decided to construct a large-scale plant to remove salt from the bay water. The plan to construct a salt-removing plant was accepted because the community  
 (A) needed increased resources. (B) had access to advanced technology. (C) had unlimited financial resources. (D) needed to ease social pressures.

SOLUTION:
A