How Might a Single Base Substitution in the Sequence of a Gene

Multiple Choice

How might a single base substitution in the sequence of a gene affect the amino acid sequence of a protein encoded by the gene, and why?

A) The amino acid sequence would be substantially altered, because the reading frame would change with a single base substitution.
B) It is not possible for a single base substitution to affect protein structure, because each codon is three bases long.
C) Only a single amino acid could change, because the reading frame is unaffected.
D) All amino acids following the substitution would be affected, because the reading frame would be shifted.