The correct option is "2 only" because adenoviruses actually have double-stranded DNA genomes, not single-stranded DNA as stated in the first point; retroviruses, in contrast, possess single-stranded RNA genomes that are reverse transcribed into double-stranded DNA during their replication cycle. The second statement is correct as adenoviruses are associated with respiratory illnesses like the common cold, while retroviruses, specifically HIV, are responsible for causing AIDS. This distinction between the types of viral genomes and their associated diseases is crucial for understanding virology and epidemiology in public health contexts, which is relevant for UPSC examination preparation.