A mutation in a plant's cell changes the gene that codes for a certain protein, and as a result the cell can no longer make the protein. The gene sequences before and after the mutation are shown in the following table.

Sequence before the mutation: A–T–T–A–T–C–A–T–A
Sequence after the mutation: A–T–T–T–A–G–A–T–C–A–T–A

What kind of mutation is shown in the table?
A.
insertion
B.
frameshift
C.
substitution
D.
deletion