Which is the first element in the periodic table to have an electron configuration in the 4th energy level?

The answer is potassium

under a microscope, cancer cells may look very different from normal cells. they often have different sizes and some may be larger than normal while others are smaller. cancer cells are often abnormally shaped and the control centre of the cell (the nucleus) may have an abnormal appearance.

i think? ?

it is the most commonly accepted one