Final Answer:
According to the selfish DNA hypothesis, TEs exist because b. they have characteristics that allow them to multiply within chromosomal DNA of living cells.
Step-by-step explanation:
The selfish DNA hypothesis proposes that transposable elements (TEs), or "jumping genes," exist because they have characteristics that enable them to multiply within the chromosomal DNA of living cells. This hypothesis suggests that TEs are primarily concerned with their own replication and spread within a genome, even if their presence does not necessarily offer a direct selective advantage to the host organism.
Option b aligns with the central idea of the selfish DNA hypothesis, emphasizing the self-perpetuating nature of TEs. Options a and c, suggesting a selective advantage or promoting the expression of beneficial genes, are not the primary driving forces behind the existence of TEs according to this hypothesis.
Option B is the answer.