The first line of defense involves which structure(s)?
O T-cells
O skin
O blood
O B-cells

answer; i believe the correct answer to the above question is ( friction)

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.

population. population is the number of people or animals in a particular place. an example of population is over eight million people living in new york city.

here is your answer hope i .