Answer:
A. Trenches were used extensively in World War I.
Explanation:
Trenches are long, narrow, and deep pathways dug along war lines to act as protection from enemy fires. The paths also allow the movement of the soldiers.
In the given letter, the soldier reveals how <em>"trenches stretch for miles"</em> but they can't move. The very slightest of movement drew enemy fire, which is dangerous. So, all the soldiers can do is lie in wait, without any movement or even making any sound. And even though the trenches cover miles of land, they cannot make any movement. But it is evident that trenches are used extensively during the First World War.
Thus, the correct answer is option A.
