When is an ellipse also a circle? A when a = b
B. when h=k
C. when a = 0
D. when the center is at 0,0)

sana makatulong

Step-by-step explanation:

a po yan

no because after the troops were pulled many blacks were killed by hangings lynchings and other cruel ways which in a way interrupted the reconstruction of the south and differed from the way abraham lincoln had an idea of reconstruction