What are neutral mutations also referred to as?

Neutral mutations are commonly referred to as silent mutations because they do not lead to any change in the phenotype or functioning of the organism. These mutations occur in the DNA sequence but do not affect the protein produced by the gene or the overall fitness of the organism. In many cases, they take place in non-coding regions of DNA or result in a codon that codes for the same amino acid due to the redundancy of the genetic code. This means that the mutation does not bring about any observable or harmful effects on the organism, hence the term "silent."

The other types of mutations in the options can lead to different outcomes. Harmful mutations would cause detrimental effects, resulting in reduced survival or reproductive success. Beneficial mutations would confer some advantage to the organism, possibly improving its adaptation to the environment. Gene mutations is a broader category that includes all types of changes within genes, not specifically neutral or silent ones.