Why were calculators invented based on numbers of protons not valid for determining atomic weights?

The image below shows a common blood pressure gauge. what does this device do? a. measures the level of oxygen present in the blood b. measures the pressure of blood when the lungs expand and compress c. measures the electrical activity of the heart d. measures the pressure of blood when the heart contracts and relaxes

Most animal cells membranes have proteins that pump ions out of the cell and potassium ions into the cell

This is the process of making a prediction based on the results of prior observations of similar events.