"Surrogate wars" also known as "proxy wars" are wars fought in a third country. The US and the Soviet Union were fighting each other in, for example, Afghanistan and Vietnam.
They preferred proxy wars, because they came without civilian victims of own population and without a distraction of the infrastructure of their own countries. In short, the two powers could compete militarily with each other without suffering the worst effects of the wars - this situation allowed them to try to defeat the other one without much risk to their own population.
The namib desert is the answer
Your questions asks why the Southern Military (Confederacy) decided to defend instead of attack.
Your answer would be C). Southern leaders thought their knowledge of Southern lands would help them defeat the Union forces.
The reason why this would be the correct answer is because the South believed that their knowledge of their land would give them the advantage in winning the war. In other words, you can say that the South "played home field." The terrain in the South was different than the terrain in the North, so they used it to get the Northerners (the Union) confused when trying to attack them. The Southerners knew where everything is: all of the bases, hiding spots, etc, and used it to a certain advantage. All in all, the Southern leaders thought that the Union would be weaker on unknown territory.