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.

A wetland habitat can continue to support the birds and fish that live there if people ___.  
 (A) drain the water away (B) flood the highest parts of the land (C) leave the land alone (D) use the land for planting crops
C

Alan is using cabbage juice to determine the relative pH of various household solutions. Which of these steps communicates the results of his investigation?  
 (A) Conduct multiple trials (B) Write down a procedure (C) Identify the materials to be tested (D) Record observations and data in a journal
D

Which set of descriptions correctly states the difference between a population and a community?  
 (A) Population: one species in an area Community: one species worldwide (B) Population: organisms in a small area Community: organisms in a large area (C) Population: living parts of an area Community: living and nonliving parts of an area (D) Population: one type of organism in an area Community: many types of organisms in an area

D