Non-functional xylem in the center of a tree trunk is

A. Summerwood

B. Sapwood

C. Heartwood

D. springwood

C. Heartwood

Explanation:

Xylem consists of both sapwood and heartwood. Sapwood is comrpsied of functioning cells whereas heartwood is made up of dead cells. The heartwood is commonly found in old trees. It stores sugar and oils. This is why its color is darker than the sapwood. It acts as a supporting structure for the old trees.

his research revealed two genetically different groups of prokaryotes, which justified splitting kingdom monera into two kingdoms. the genetic and cellular differences were so great, that these two kingdoms were eventually placed into different domains in the current three-domain system.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link: