b) SUBTLETY refers to the risen body's ability to penetrate solid matter.

Does the human body have the ability to pass through matter?
Our bodies have the ability to pass through air and water by displacing the molecules of air or water. Further, we live and move in an electro-magnetic field, e.g. sunlight, some of which we reflect and absorb as heat. Our soul is immersed in energy/matter and it acts within and through the realm of living and non-living matter.

On Easter Sunday evening "when the doors were locked" because the Apostles feared the Jews, Jesus came and stood among them (Mt. 20:19), in other words, Jesus passed through solid matter to enter the room. Refering to the human body, St. Paul tells us:

"It is sown a natural body;
it is raised a spiritual body."
( Cor. 15:44 )

There is no doubt that the body will take on spiritual qualities (like iron placed into the fire takes on the qualities of fire) but it will not become spirit as attested by Christ (Lk 24:39). It will be able to pass through solid matter as light can pass through glass.

How can we understand the nature of the spiritual body?
According to the scientific superstring theory matter at its deepest level is composed of strings or loops of vibrating energy a hundred billion billion times smaller than an atomic nucleus. Each of these strings vibrates with a unique frequency giving rise to its mass and force changes. To quote Brian Greene: "The microscopic landscape is suffused with tiny strings whose vibrational patterns orchestrate the evolution of the cosmos." 19 This is the music of the Universe.

Now, the transfigured soul, as the essential form of the body, will have complete mastery over its body. It may be able change the vibrational patterns of its matter so as to become transdimensional. "In heaven the body will be to the soul like a violin in the hands of a masterful musician. Filled with unspeakable glory, the soul will inform and activate the body, raising it to sublime heights, which 'eye has not seen, nor ear heard, nor has it entered into the heart of man' to imagine."(kofc.org/faith/cis/034/risglor.cfm)

The Risen Life will surely be an adventure to look forward to.