The pH of the following substances can be ranked from low to high as follows:

1. Stomach acid (pH 1-2): Stomach acid is highly acidic due to the presence of hydrochloric acid (HCl). It helps in breaking down food and killing harmful microorganisms.

2. Urine (pH 4.6-8): Urine can have a pH range from slightly acidic to slightly alkaline, depending on various factors such as diet, hydration level, and kidney function.

3. Blood (pH 7.35-7.45): Blood is slightly alkaline and maintains a narrow pH range to ensure proper functioning of enzymes, cells, and organs.