Concept:The correct preposition completes the meaning of testifying in opposition to someone.Explanation:The sentence describes a woman who refused to give evidence in court against her husband.The phrase "testify against" means to give testimony that opposes or incriminates another person."Against" expresses opposition or disagreement in this legal context.The other options, "from," "in," and "at," do not form the correct collocation with "testify" here.Answer:D. Against.