For an explanation of the Questions and Actions system, please refer to the standalone page for the Question object, included in this Wave 1 of the X-Particles manual.
Questions tab menu.
Clicking this button will add a Question object to the Object Manager and will automatically add it to the Questions list.
Particle Radius Question object in the Questions list.
Once a question has been added to this list, it can be set up to trigger certain effects or to activate/deactivate modifiers.
In this animation a Question object is added, using the Add Question button, relating to the particle age. The result is that particles over 60 frames of age are changed from Arrow to Box.