To speed up the action of the particles in a solid mass, Mora should consider breaking it apart. When a solid mass is broken apart into smaller pieces, the surface area increases, allowing for more effective movement and interaction of the particles. This can lead to an increase in the speed of the particles and enhance the overall activity in the solid.
The other options, such as adding more mass, using an inhibitor, or lowering the activation energy, do not directly contribute to accelerating the action in the same way. Inhibitors would slow down reactions, while lowering activation energy is more relevant in the context of chemical reactions rather than the kinetic behavior of solid particles.