What is the test for establishing liability on a negligence theory?

"'In order to establish liability on a negligence theory, a plaintiff must prove duty, breach, causation and damages.' [Citation.] The duty element is the defendant's legal duty to protect the plaintiff from harm. [Citation.] Whether a duty to the plaintiff exists in any particular negligence case is a question of law. [Citation.] Courts use the concept of duty to restrict the otherwise potentially unlimited liability flowing from a negligent act. [Citation.] A determination that a duty exists amounts to a policy decision that a particular plaintiff should be protected [citation], i.e., 'that, in cases of a particular type, liability should be imposed for damage done' [citation ]." (Smith v. Freund (2011) 192 Cal.App.4th 466, 472.)