The answer to this question would be labile.
A permanent cell is the one that will not divide after fully developed. This includes the heart and brain cells. That is why when these organs damaged there will be a permanent loss of function.
Stable cell only divides in some occasion. The example would be liver cells or kidney cells.
The sun is a source of energy
I think what they rely on is there experiment and how they do it
Carbohydrate is the answer
