B
Step-by-step explanation:
Mutations are any changes to the sequence of nucleotides on DNA. These mutations can be caused by environmental factors such as UV rays from the sun of mutagens like arsenic. These mutations cause a change in the protein that is translated from the DNA. Some mutations are lethal while some are silent.
Mutations though very rare, but also very significant since they diversify alleles hence giving a base on which natural selection pressures can act on to help a population adapt to changes in the environment.