Step 1: Understand sound.
Sound is a mechanical wave. It needs a material medium with particles to travel.
Step 2: Why a medium is needed.
Sound moves through compressions and rarefactions of particles. Without particles there is nothing to vibrate.
Step 3: The vacuum.
A vacuum has no particles at all, so sound cannot travel through it. That is why astronauts need radios in space.
Step 4: The other media.
Sound travels through solids, liquids and gases. In fact it is fastest in solids: $V_{solid} > V_{liquid} > V_{gas}$.
Step 5: Conclude.
Sound cannot travel through a vacuum.
Answer: Vacuum