When the wife claims the top shelf is unavailable, the husband points out the

• A. A locked box
• B. Dusty cobwebs
• C. Hammers and nails on it
• D. Hidden shelf

Answer: (C)

When something is described as unavailable, the clearest way to judge it is by what’s physically present on or in that space. The top shelf isn’t just empty or closed off; it’s being used as a place for tools. The husband points out hammers and nails on it, showing that this shelf is actively occupied for storage, which explains why it’s unavailable for the wife’s use at that moment. The other possibilities rely on conditions that aren’t evidenced here—like a locked box, which would require a lock; dusty cobwebs, which suggest neglect; or a hidden shelf, which would imply there’s another space to use instead. So the hammers and nails on the shelf provide the direct, observable reason it’s not available.