According to the passage, which of the following is true concerning the development of GHBs
A． A lack of electromagnetic energy prevents the GHBs from becoming visible at the earliest stage of their existence. B． Photon density precludes the manifestation of GHBs to observers as the GHBs initially develop. C． There is a dearth of luminosity that makes GHBs impossible to observe from longer distances, but not shorter ones. D． The viewer's timescale tends to be to compressed at the earliest phase of GHBs' development to allow them to be observed. E． GHBs tend to move at too slow a velocity to be observed as the initially develop.