The answer is B: Stonehenge.
Explanation for each option:
a. Christo and Jeanne-Claude's The Gates: This was a temporary installation in Central Park, New York City, which was on display from February 12, 2005, to February 27, 2005. It no longer physically exists.
b. Stonehenge: This prehistoric monument located in Wiltshire, England, still physically exists and is one of the most famous landmarks in the United Kingdom.
c. Diego Rivera's Man at the Crossroads Looking with Hope and High Vision to the Choosing of a New and Better Future: This mural was commissioned for the Rockefeller Center in New York City but was destroyed in 1934 before it was completed due to its controversial content.
d. Richard Serra's Tilted Arc: This was a large-scale public sculpture installed in Federal Plaza, New York City, in 1981. It was removed and destroyed in 1989 following public controversy and legal battles.
e. all of the other answers: This option is incorrect because not all the listed artworks still physically exist. Only Stonehenge remains intact.