What is the general weight threshold, per the standard rule, at which most hazardous materials require placarding?

Correct answer to question 119 (Hazardous Materials): 1,001 pounds or more of the material, aggregated per placard-required category

Why

For most hazard classes under table 2 of the placarding rules, placards are required once the aggregate gross weight of hazardous materials in that category reaches 1,001 pounds or more.