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.

A scientist is searching for areas where new solar systems might form. What feature is the scientist looking for?  
 (A) a star similar to our Sun (B) a cloud of dust and gas (C) an oxygen-rich atmosphere (D) a gravitational acceleration of 9.8 m/sec2
B

Which of the following best describes a mineral?  
 (A) a solid natural material with a crystal structure (B) a material that was once living but has decayed (C) a liquid chemical used to make soil more fertile (D) a nutrient produced by plants that other organisms need
A

Iron oxide, also known as rust, is formed when iron chemically combines with oxygen. Which term best describes iron oxide?  
 (A) element (B) mixture (C) solution (D) compound

D