Why is it necessary for the stomach contents to be so acidic? how does the stomach protect itself from digestion?

Can someone me with 3 and 4 plz. this is for masteries test.

Which substance has non polar covalent bonds

Many free radicals combine to form molecules that do not contain any unpaired electrons. the driving force for the radical–radical combination reaction is the formation of a new electron‑pair bond. consider the chemical equation. n(g)+no(g)⟶nno(g) n(g)+no(g)⟶nno(g) write lewis formulas for the reactant and product species in the chemical equation. include nonbonding electrons. n(g)n(g) select draw rings more erase select draw rings more erase select draw rings more erase n no(g)