What is one way that a frameshift mutation could occur?

two nucleotides are deleted two nucleotides are deleted two nucleotides are substituted two nucleotides are substituted three nucleotides are inserted three nucleotides are inserted three nucleotides are deleted

A frameshift mutation could occur if three nucleotides are deleted or inserted. This mutation would shift the reading frame of the genetic code and result in a completely different sequence of amino acids in the protein being produced.