Which type of mutation is characterized by a simple substitution of one base for another?

The correct identification of a mutation characterized by a simple substitution of one base for another is indeed a base substitution mutation. This type of mutation refers specifically to any alteration in the DNA sequence where one nucleotide (the basic unit of DNA) is replaced by another.

Within this category, there can be further classifications, such as missense mutations, silent mutations, and nonsense mutations. A missense mutation occurs when the base substitution leads to a different amino acid being incorporated into a protein, potentially altering its function. A silent mutation results in the same amino acid being produced because of the redundancy in the genetic code, meaning the change does not affect the protein at all. A nonsense mutation causes a premature stop codon to form, which can lead to truncated proteins that are usually nonfunctional.

Understanding that "base substitution mutation" encompasses all these possibilities is why it is the most accurate description in this context.