Final answer:
All the listed respiratory systems (tracheal system, gills, and diffusion) are indeed used by invertebrates to breathe. The tracheal system involves a network of tubes for breathing in insects, gills are used by aquatic invertebrates, and diffusion is employed by simpler invertebrates like flatworms.
Step-by-step explanation:
Invertebrates utilize various respiratory systems, and among those mentioned, none is incorrect as they are all used by invertebrates to breathe. The tracheal system is predominantly found in insects and some arachnids and myriapods. This system involves a network of tubes made of chitin that carry oxygen directly to the body's tissues. Insects have spiracles along their bodies that open into these tubules, allowing for gas exchange.
Gills are another respiratory structure used by aquatic invertebrates, such as mollusks and some arthropods, to extract oxygen from water.
Diffusion is a simpler form of respiration used by smaller or less complex invertebrates, such as flatworms, where gases are exchanged directly across the body surface.