Answer :
Final answer:
Smokeless powder is not safe to use in standard muzzleloaders because it generates dangerously high pressures, unlike black powder and black powder substitutes which are specifically designed for such firearms.
Explanation:
The type of powder that should NOT be used in a STANDARD muzzleloader is b) Smokeless powder. Smokeless powder produces much higher pressures than black powder or its substitutes and can cause a traditional muzzleloader to explode, which would be extremely dangerous. Standard muzzleloaders are designed to be used with black powder, or black powder substitutes like Pyrodex or Triple Seven, which are formulated to mimic the burn rate and pressure curve of black powder. Always consult your firearm's manufacturer recommendations for the correct type of powder to use.