Answer:
B. Res ipsa loquitur
Step-by-step explanation:
Res ipsa loquitur will be most helpful against the designer. Res ipsa loquitur means the thing speaks for itself. It is appropriate in situations where an injury does not usually occur unless someone was negligent and the plaintiff does not know which of the defendants caused the injury.
(A) is not correct because the doctrine of respondeat superior imposes vicarious liability on an employer for the tortious conduct of its employee. That doctrine would be helpful against the building company for any negligence by its employees but not against the designer because the workers were not the designer's employees.
(C) and (D) are incorrect because the doctrines of contribution and indemnity pertain to how the responsibility of the loss is apportioned or shifted among the defendants after the plaintiff has recovered his judgment. They are not relevant to the homeowner's right.