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: For many years, scientists have found fossils in rock layers in all parts of the world. Eventually scientists discovered that many of the rock layers showed the same pattern of older fossils being located in deeper rock layers and younger fossils being located in shallower layers. This discovery is an example of how scientific knowledge changes as  
 (A) fossils are preserved in different ways. (B) conclusions about fossils are revised into questions. (C) fossils are formed in different areas. (D) new fossil evidence is reviewed.

SOLUTION: D

PROBLEM: Weather forecasts are more accurate today than in the past due to  
 (A) global warming (B) air-quality control (C) plate tectonics (D) use of images from space

SOLUTION: D

PROBLEM: How has burning fossil fuels most caused a decline to the quality of air that people breathe?  
 (A) by adding particle pollution (B) by creating a hole in the ozone layer (C) by causing acid precipitation to fall (D) by increasing the levels of carbon dioxide

SOLUTION:
A