Which one of the following best describes the main idea in Paragraph 2?

Correct Answer: It explains why castles were first built in England and the military purposes they served.

Explanation:

The main idea of a paragraph captures its central focus and primary purpose. Paragraph 2 focuses specifically on the origins of castles in England following the Norman Conquest and highlights how they were strategically constructed and utilized for defense and military control.

Let's evaluate why the selected statement best describes Paragraph 2:
1. Focus on Castle Origins: It addresses the initial reasons behind building castles in England, establishing the historical context.
2. Military Function: It highlights the tactical and military significance of these fortifications in securing dominance and defensive capabilities.

Therefore, the option stating that "It explains why castles were first built in England and the military purposes they served." is the correct summary of Paragraph 2.