'Hit the nail on the head' means
AMake a costly silly mistake
BHammer a nail very correctly
CStrike someone on the head
DDescribe exactly what is right
Answer & Solution
Correct answer: D. Describe exactly what is right
1. Idiom: precisely identifying the right cause or answer.
2. Literal nail hammering is the trap.
3. Hence option A.
_Source: jkchrome.com SSC Idioms and Phrases PDF (Mistral OCR), section on common idioms_