Option 1 -> A diligent investigator wouldn't ask "evasive" (avoiding) questions or try to "confuse" details - this contradicts their purpose.
Option 2 -> "Irrelevant" questions and "obscuring" details would be counterproductive for someone trying to solve a case thoroughly.
Option 3 -> "Incisive" means sharp and penetrating; "elicit" means to draw out or obtain information - perfectly describes a thorough investigator's approach.
Option 4 -> "Vague" questions are unclear and wouldn't help "exaggerate" (overstate) details - this doesn't align with diligent investigative work.
Hence, Option 3: incisive, elicit -> A diligent investigator asks sharp, penetrating questions designed to draw out and obtain accurate details from the suspect, which is the hallmark of effective interrogation -> correct