Final answer:
The author seems to feel sorry for the high casualty rate of British soldiers. Therefore, the correct option is D.
Step-by-step explanation:
In document C of the Battle of the Somme, the author's perspective on the British soldiers who died in battle can be inferred from the given information. The author describes the tremendous casualties suffered by the British soldiers, stating that tens of thousands were killed in the first day alone.
This suggests that the author may feel sorry for the high casualty rate of the British soldiers. Therefore, option D) The author seems to feel sorry for the high casualty rate of British soldiers, is the most accurate answer.