Answer:
I believe it will be D. all of the above.
Explanation:
Snake goes to frog frog goes to bug bug goes to leaf and leaf goes to soil
The major histocompatibility complex (MHC<span>) is a set of cell surface proteins essential for the acquired immune system to recognize foreign molecules in vertebrates, which in turn determines histocompatibility. ... The human </span>MHC<span> is also called the </span>HLA<span> (human leukocyte antigen) complex (often just the </span>HLA<span>).</span>
The brain and spinal cord are both structures of the central nervous system.