C. Arachnida.
hope it's correct.
The myelin sheath covers most of the axon. It is important because it helps to protect the axon and speed up the neuron firing process by decreasing the amount of time in the axon.
Known as the cell’s “command center,” the nucleus is a large organelle that stores the cell’s DNA (deoxyribonucleic acid). The nucleus controls all of the cell’s activities, such as growth and metabolism, using the DNA’s genetic information. Within the nucleus is a smaller structure called the nucleolus, which houses the RNA (ribonucleic acid). RNA helps convey the DNA’s orders to the rest of the cell and serves as a template for protein synthesis.
