Final answer:
When pointing your finger at a computer screen, it is touching air, as the space surrounding the computer screen in a typical room setting is filled with air, not a vacuum or plasma.
Step-by-step explanation:
When you point your finger at the computer screen, your finger is touching air. This is because the computer screen is typically surrounded by air, which is the medium in the room. There is no vacuum as that would imply a space entirely devoid of matter, which is not the case in normal circumstances. Furthermore, plasma is a state of matter found in situations such as stars or neon signs, not standard for the environment around computer screens. Your finger is definitely touching something, so option '3) nothing' is incorrect.