Please choose the correct ending to complete the given sentence: Education and Communications: [header] How to study the chemistry and physiological roles of calcium ions in the body [title] Understand the difference between the metallic and ionic forms of calcium. [step] The element calcium follows the trend in properties that is seen with magnesium, sodium and potassium elements. Namely, it is toxic to mammals in its metallic form, while it is benign in its ionic form.

Ending1: In order to really understand the balance between these two substances, study periodic urine division to find out the balance between two components of magnesium ions. [title] Study periodic formula formulas to complete the formula for magnesium ions. Ending2: The characteristic start and end voltage adjacent to the nodes of platinum and magnesium ions is the reverse. In order to absorb magnesium ions, plasma cells are needed to be able to filter them and charge them. Ending3: [title] Understand carbohydrates which contain the minerals, fatty acids, vitamins, minerals and nutrients contained in them. [step] These minerals and fatty acids are easier to digest than fatty acids. Ending4: Actually, calcium ions are not only benign but also essential for the metabolism of the body. [title] Study the use of calcium by the body.

Answer format: ending1/ending2/ending3/ending4