Correct Answer:
B. USA
Explanation:
The Hoover Dam is a monumental concrete arch-gravity dam on the Colorado River, located on the border between Nevada and Arizona in the United States. Built during the Great Depression between 1931 and 1936, it was originally known as Boulder Dam but was renamed after President Herbert Hoover in 1947.
### Important Facts:
- River: Colorado River.
- Lake Created: Lake Mead, the largest reservoir in the US by volume.
- Purpose: Provides flood control, water supply/irrigation, and hydroelectric power generation.