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.

Which of these is an environmental benefit of converting to solar energy?  
 (A) a decrease in air pollution (B) an increase in the cost of energy (C) an increase in the use of fossil fuels (D) a decrease in electrical energy production
A

A student plans to design a new toothpaste tube that will give the same amount of toothpaste every time it is squeezed. Which should the student do first when designing the new tube?  
 (A) make a data table of amounts of toothpaste (B) gather building materials (C) create models of old toothpaste tubes (D) draw a few possible solutions
D

Which phase of the Moon occurs after a waxing gibbous?  
 (A) waning gibbous (B) waxing crescent (C) full moon (D) new moon

C