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 is the best piece of equipment to determine the topography of the United States?  
 (A) radar (B) compass (C) satellite (D) radio
[A]: C


[Q]: Weather forecasts are more accurate today than in the past due to  
 (A) global warming (B) air-quality control (C) plate tectonics (D) use of images from space
[A]: D


[Q]: Magnesium bromide is one of the most abundant compounds found in sea water. Which formula correctly represents magnesium bromide?  
 (A) MgBr (B) MgBr_{2} (C) Mg_{2}Br (D) Mg_{3}Br_{2}
[A]:
B