If a person has a blood-calcium (Ca) level of 8 mg/100 mL of blood, which of the following mechanisms does the body use to maintain blood-calcium homeostasis?
A The kidneys take up more Ca? and release vitamin D.
B The bones release Ca?
C The intestines increase reabsorption of Ca?
D All of the above

The kidneys take of up more Ca2+ and release vitamin D. The bones release Ca2+. The intestines increase reabsorption of Ca2+.

water is a polar molecule. a chemical bond is a force of attraction between atoms or ions. bonds form when atoms share or transfer valence electrons. atoms form chemical bonds to achieve a full outer energy level, which is the most stable arrangement of electrons. so, false

explanation:

in h2o molecule, two water molecules are bonded by a hydrogen bond but the bond between two h - o bonds within a water molecule are covalent. the greater the electronegativity difference, the more ionic the bond is. bonds that are partly ionic are called polar covalent bonds. nonpolar covalent bonds, with equal sharing of the bond electrons, arise when the electronegativities of the two atoms are equal.