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.

Which of the following was invented by Benjamin Franklin?  
 (A) bifocal lens (B) telescope lens (C) telephone (D) camera
A

The prairie grass ecosystem once had a deep layer of topsoil which was protected by the grasses that covered it. Removal of these grasses for farmland is causing the soil to be eroded mainly by  
 (A) wind and rain. (B) animal movement. (C) crops grown in the soil. (D) increased temperatures.
A

Which of the following do water (H2O), rust (Fe2O3), and salt (NaCl) have in common?  
 (A) Water, rust, and salt are atoms. (B) Water, rust, and salt are mixtures. (C) Water, rust, and salt are elements. (D) Water, rust, and salt are compounds.

D