Which cells are considered immortal?
neurons
blood cells
cardiac muscle cells
stem cells

"Normal stem cells and germ cells can also be said to be immortal (when humans refer to the cell line). Immortal cell lines of cancer cells can be created by induction of oncogenes or loss of tumor suppressor genes."

Stem cells are considered as immortal as they have the ability to divide and differentiate into a new type of cell but at the same time keep on producing the original stem cell as well.This means when the stem cells divide they produce two cells - one of the cells differentiates and produce a new type of cell whereas the other cell becomes the stem cell.Thus the stem cells are able to replenish themselves and are considered immortal.

The answer is magnitude measures the effects of an earthquake on the area , while the intensity measures the strength of an earthquake.