What Did the Term "White Man's Burden" Mean

What did the term "white man's burden" mean?

A) Domination of nonwhites by white people was necessary for the progress of civilization.
B) Imperialism required long absences from friends and family back home.
C) The only way to ensure American victory in the Philippine War was for white soldiers to accept black fighters into their ranks.
D) It was a tongue-in-cheek reference coined by Mark Twain to describe atrocities committed by American troop against Filipinos.
E) It referred to the heavy kit U.S. soldiers had to carry while on duty.