Why are retroviruses considered a special class of viruses?

it has one origin of replication, but it proceeds in two directions - d)

i don't know. if i were you, i would search it up online : d

emerging idea only occurs as a raw idea that could appear out of nowhere. meanwhile, to reach scientific consensus , that idea must be structured and tested over and over again through various experiments. the scientific consensus transforms the raw idea into idea that is more reliable through the process of scientific elimination.