Which statement BEST describes the role and importance of mobile genetic elements in genomes?

A) Mobile genetic elements almost always have either neutral or deleterious consequences for their host.
B) Mobile genetic elements are largely beneficial to hosts because they introduce new phenotypic variation into a population via transposition and/or duplication of important genes.
C) Mobile genetic elements can have deleterious, neutral, OR beneficial consequences for the host organism, and all three kinds of outcomes are common.
D) Mobile genetic elements are especially important for plant genomes such as the tomato, but they are not present in most animal genomes.