"The White House Plumbers"
"The Plumbers," as they were commonly termed, were a White House Special Investigations Unit, established by President Richard Nixon in July, 1971. This was a reaction after Daniel Ellsberg had leaked what became known as <em>The Pentagon Papers </em>to the <em>New York Times</em>, and the <em>Times </em>began publishing excerpts from them in June, 1971.
Members of the Plumbers unit were responsible for the Watergate break-ins that resulted in the scandal that eventually brought down the Nixon presidency.
Serbia wasn't included in the central powers.
So the correct answer is D.
The members included Germany, Austria-Hungary, the Ottoman Empire, Bulgaria and their territories.
Hope this helped!(:
South Vietnam surrendered after Saigon fell.