15. B
16. D
17. F
18. E
19. A
20. C
Pythagoras study perfect intervals.
Board of Governors-<span>directing </span>
On August 25, 1916, President Woodrow Wilson signed the act creating the National Park Service, a new federal bureau in the Department of the Interior responsible for protecting the 35 national parks and monuments then managed by the department and those yet to be established.