Answer
Neon can be liquefied by compressing it.
Work Step by Step
When something is compressed, it means that the volume that it occupies decreases. From PV=nRT, we recall that there is an inverse relationship between volume and pressure, so as volume decreases, pressure increases. The diagram shows that Neon is liquid at higher pressures when at 25 K, so compressing Neon to make pressure increase will work.