How Can a Plaintiff Prove That a Defect Exists in a Product

Multiple Choice

How can a plaintiff prove that a defect exists in a product?

A) Through the introduction of expert testimony,which is always required,and sometimes circumstantial evidence.
B) Through evidence other than expert testimony,which is never reliable because experts are paid.
C) Through the introduction of expert testimony only.
D) Through the introduction of expert testimony and/or circumstantial evidence.
E) Through the introduction of both expert testimony and circumstantial evidence.