The correct answer is (d).
Somatic cells are the cells that make up the body, while germ cells are the cells that produce gametes (eggs or sperm). Mutations in somatic cells do not affect the offspring, but mutations in germ cells can be passed on to the next generation.
Mutations are changes in the DNA sequence. They can be caused by errors in DNA replication, exposure to mutagens (such as radiation or chemicals), or viruses. Most mutations are harmful and cause genetic diseases, but some mutations can be beneficial. Beneficial mutations can give an organism an advantage over other members of its species, and over time, these mutations can lead to evolutionary change.
Mutations are essential for evolution because they provide the raw material for natural selection. Natural selection is the process by which organisms that are better adapted to their environment are more likely to survive and reproduce. Beneficial mutations are more likely to be passed on to the next generation, while harmful mutations are less likely to be passed on. Over time, this process can lead to the evolution of new species.
In conclusion, mutations in germ plasm DNA are the only mutations that can be passed on to the next generation and therefore have the potential to lead to evolutionary change.