What are the WHMIS classifications, and their symbols?

There are 6 different WHMIS classifications, which are depicted by classes A through F. Several of these have multiple sections and subsections. They are as follows:

Class A. Compressed Gas
Materials which are normally gases, contained under pressure.

Class B. Flammable/Combustible Material
Flammable materials burn at temperatures below 37.8 °C (100°F). Combustible materials burn at temperatures of 37.8°C–93.3°C (100°F–200°F). Reactive flammable materials spontaneously combust when combined with air/water, or react with air/water to make flammable gases.
B1. Flammable Gases
B2. Flammable Liquids
B3. Combustible Liquids
B4. Flammable Solids
B5. Flammable Aerosols
B6. Reactive Flammable Materials

Class C. Oxidizing Material
Contributes to the combustion of another material by producing oxygen or another oxidizing agent,regardless of whether the material itself is combustible;
or the material is an organic peroxide that contains the bivalent O-O structure.

Class D. Poisonous and Infectious Material
Class D1. Materials Causing Immediate and Serious Toxic Effects
Effects to health are usually fast-acting, but can also be long-term.
D1A. Very Toxic Material
D1B. Toxic Material
Class D2. Materials Causing other Toxic Effects
Effects are usually slow acting and may be temporary.
D2A. Very Toxic Material
D2B. Toxic Material
Class D3. Biohazardous Infectious Materials
An organism that causes disease in humans and animals.

Class E. Corrosive Material
Causes severe burns to human tissue, and other materials including metals.

Class F. Dangerously Reactive Material
A material that undergoes vigorous polymerization, decomposition or condensation; reacts with water to release a toxic gas; or self-reacts under shock, increased pressure or temperature.