答案：A

解析：

To be "cognizant of" something is to be informed about or aware of it. The sentence indicates that the reporter's interview techniques were allegedly unethical — that is, the reporter was accused of using techniques that do not conform to approved standards. If the editor was unaware of the reporter's journalistic practices, he could plausibly deny any knowledge of — and responsibility for — her techniques, whether ethical or unethical. Therefore, it makes sense to suggest that the editor would claim that he was cognizant of only the reporter's finished work and not her journalistic practices.