Digestive. This also includes the intestines.
The answer is (3) pH 3 to pH 1. The pH is related to the concentration of H3O+ with the relationship: pH = -lg c(H+). So when concentration of H3O+ increase, the pH will decrease. And decrease 2 when when increase hundredfold. Because 100=10^2.
Carbon atoms in single bonds rotate freely. Rotation can occur because the heaviest electron density in the σ bond exists along an imaginary line between two carbon nuclei. Rotation does not change this electron distribution; the bond strength remains constant throughout rotation.
Lithium and nitrogen have the same electron energy levels, actually 2 levels.
