Light Is Increasingly Redshifted near a Black Hole Because

Light is increasingly redshifted near a black hole because

A) the photons are moving away from us very quickly as they are sucked into the black hole.
B) the photons are moving increasingly faster in order to escape the pull of the black hole.
C) time is moving increasingly slower in the observer's frame of reference.
D) the curvature of spacetime is increasingly stretched near the black hole,which in turn stretches the wavelengths of the photons.