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]: If an atom of hydrogen gives up one electron, what is its overall charge?  
 (A) -1 (B) +1 (C) -2 (D) +2
[A]: B


[Q]: Nearly 100 years ago, a large volcano erupted in the South Pacific. The following year, Boston recorded measurable snow every month of the year, and most of the Northern Hemisphere experienced a cold summer. Which explains how these two events were related?  
 (A) The eruption intensified the greenhouse effect. (B) Lava flow from the eruption caused a temporary increase in Earth's total heat energy. (C) The eruption caused damage to the ozone layer. (D) Air pollution from the eruption caused a decrease in the amount of solar energy reaching Earth.
[A]: D


[Q]: According to a pH scale, which pH would be the strongest acid?  
 (A) 3 (B) 6 (C) 9 (D) 12
[A]:
A