Exam CFE - Law topic 1 question 24 discussion

I'am confused btw A & D (definitely not C) A - Because, the questioning party is attempting to make Greg appear incompetent or unprepared by focusing on a very narrow, tangential issue that Greg has not spent much time on. They are trying to create the impression that Greg's expertise is limited, despite his work on other, more relevant aspects of the case. D - Because, The sounding board technique is a cross-examination strategy where the questioning party first establishes that the expert is knowledgeable in one area, then shifts the focus to a related but less familiar topic to make the expert appear uninformed or less credible.