HELP.............. PLEASE ..........................................?????????????????? 10 POINTS !!!!

On June 19, 1865, a holiday called Juneteenth began in Texas. Each year, African American in Texas and other parts of the United States celebrate Juneteenth to mark the .........????

A. first day of summer.
B.first harvest of the year.
C.end of the American civil war.
D.end of slavery in the United States