Sounds like the answer is D
The support trench served to house reinforcements, and supplies, for the front line troops that could be quickly transported to the front line trench. A third type of trench was commonly referred to as a reserve trench and was found dug "several hundred yards" behind the support and front line trenches.
During the golden age of the Islamic empire, many advancements were made in lots of different areas. New forms of art were created, and new ways of thinking, including the beginnings of the mathematic system of algebra, emerged as well. So it's A.
An example can be the Missouri Compromise. According to it, a line was made and it was decided which countries could have slaves and which not. Now, it was considered to be a relatively good compromise because it helped the Union stay together, but watching it from the modern times it was most certainly not a good compromise because any compromise that establishes slavery anywhere is definitely not a good one.
A historian has to out things chronological order so we know what happened first
