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.

[Q]: Which layer of Earth is the source of lava that erupts from volcanoes?  
 (A) asthenosphere (B) inner core (C) outer core (D) lithosphere
[A]: A


[Q]: 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
[A]: D


[Q]: A population of deer recently increased in size. Which most likely could have caused the deer population to increase?  
 (A) A disease was spreading. (B) Their habitat was destroyed. (C) Food sources were hard to find. (D) Their predators were disappearing.
[A]:
D