Final answer:
The main idea of this article centers on the importance of remembering September 11, 2001, and honoring those who were lost in the attack, as suggested in option D.
Step-by-step explanation:
The main idea of this article is represented by option D. The phrase 'It is important to remember September 11, 2001, and those who were lost' encapsulates the primary thrust of the theme, emphasising remembrance and honouring those who perished in the tragic event. It's not solely about the physical description of the towers before or after the attack, or the fear that led to peace. The focus is on the importance of memory and respect for lost lives.
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