There are many repeats in the human genome, which cause many problems for genome assembly. Where do these repeats come from? Do you believe they are junk DNAs?
a) They come from gene duplications and transposable elements. No, they are not junk DNAs.
b) They come from environmental factors. Yes, they are junk DNAs.
c) They are errors in the sequencing process. No, they are not junk DNAs.
d) They come from viral infections. Yes, they are junk DNAs.