The answer should be the third option "number of protons and neutrons." The atomic mass of a element is equal to the amount of protons, and neutrons added together in that element. So for example if we are trying to find the atomic mass of hydrogen you would add the total amount of protons and neutrons together to find it's mass although it doesn't equal the exact amount of it's mass but it's close.
Hope this helps.
Technically, the black widow spider is the deadliest spider despite it's size, due to it's overwhelmingly potent venom, which can and will kill a human if no medical attention is sought out for the person bit.
The cell because they are moving from high to low concentration
