Which of the following is a doctrine available to defendants whereby a defendant may avoid liability by establishing that the plaintiff voluntarily and unreasonably encountered the risk of the actual harm that the defendant caused?
a. Last-clear-chance doctrine.
b. Assumption of risk doctrine.
c. Contributory negligence doctrine.
d. Res ipsa loquitur.
e. Negligence per se.

Hegyes was driving her car when it was negligently struck by a unjian enterprises truck. she was injured, and an implant was placed in her body to counteract the injuries. she sued unjian, and the case was settled. two years later hegyes became pregnant. the growing fetus pressed against the implant, making it necessary for her doctor to deliver the child 51 days prematurely by cesarean section. because of its premature birth, the child had a breathing handicap. suit was brought against unjian enterprises for the harm sustained by the child. was the defendant liable?