What applies to a provider of defective or hazardous products or services that unduly threaten...

Strict liability applies when a manufacturer or service provider is held legally responsible for damages or injuries caused by a defective product or service, regardless of fault or intent. This type of liability is often associated with consumer protection laws, where the focus is on the danger posed to the user rather than negligence on the part of the provider.

Plaintiff (B) is the party bringing the suit.

Defendant (C) is the party being sued.

"None of the above" (D) is incorrect since "Strict liability" is the correct legal principle.