instruction:
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.
question:
Kim lost her hammer outside. When she found it a few months later, some parts of the metal were covered with flaky, brown rust. Which type of change occurred when rust formed on the hammer?  
 (A) chemical (B) electrical (C) thermal (D) physical
answer:
A


question:
The excessive use of nitrogen-based fertilizers causes runoff that increases the nitrogen content of lakes and bays. These nitrogen compounds directly affect the aquatic ecosystems by  
 (A) interfering with the water cycle. (B) decreasing the predator population. (C) increasing the rate of algae growth. (D) causing aquatic animals to grow larger.
answer:
C


question:
A student finds that an unidentified mineral sample can scratch gypsum but is unable to scratch quartz. The student has made an observation about which property of the sample?  
 (A) luster (B) hardness (C) density (D) reactivity
answer:

B