What's the layer of material found at the innermost part of wood?
a. sapwood
b. cork cambium
c. vascular cambium
d. heartwood

If you opened a tree and wanted to see what is in the middle, you would see that it is D. Heartwood. It is very coveted because it often used in creating artistic things or in making high quality furniture and wooden floors and there can only be a limited amount of heartwood per tree so getting it can be bad for the environment if you're not careful.