When a sentence is written it's either in active or passive voice. Active voice describes a sentence in which the subject (Kevin) is performing an action stated by the verb (asked) that affects the object (Dennis). Passive voice describes a sentence where the action is performed 'by the' subject, the subject is now the object and vice versa. The tense of the sentence remains the same, and the form changes. When the given sentence is changed to passive voice, the verb 'asked' is in simple past, and 'was' is added to the participle 'asked' or else the meaning of the sentence changes, hence option C is correct. Option A is incorrect because 'was' does not go with 'been' because 'been' is always preceded by 'has', 'had' or 'have'. Option B is incorrect because the phrase "was being asked" is in past continuous whereas the original sentence is in simple past. Option D is incorrect because 'has been asked" is in present perfect tense.