Answer :
The answer would be D concrete. The Eiffel Tower is built of wrought iron, not steel, and while aluminum and copper may have been used for electrical purposes or other minor details, they were not essential for the tower's construction. Instead, giant concrete slabs enabled Eiffel to built the over 7,000ton structure without it sinking into the ground or tilting.
The concrete building developed in the 1800s allowed Gustav Eiffel to erect the world's tallest structure in Paris, in 1889.
