When the dna'sentence' changes from the fat catate the rat to the atc ata tet her atc.
what type of mutation is this?

Frame shift insertion mutation or Frame shift deletion mutation.

Explanation:

The DNA sentence THE FAT CAT ATE THE RAT

In the above sentence if we delete the letter F and insert letter C and rearranging the sentence to make a triplet word then the sentence change into

THE ATC ATA TET HER ATC

The conclusion of the above exercise is very obvious. Insertion or deletion of one or two bases changes the reading frame from that point. However, such mutations are referred to as frameshift insertion mutation or frameshift deletion mutations.

answer; motor (efferent)neurons;