Ginger is considered to be a stem, not a root. Why?

Rhizome of ginger is like roots of other plants grown underground. Despite this fact ginger is a stem not a root - Justify.

Why potato tuber is considered as a stem ? Although it is an underground plant part.

Why are viruses considered to be a biologist's puzzle?

Which is considered to be earth's protective umbrella ? Why?

Why is euploidy considered to be advantageous to both plants and animals?

Which is considered as the major cause of global warming? Why?