The binary compounds of oxygen with other elements are called oxides. They are classified depending either upon their acid-base characteristics or on the basis of oxygen content. (a) Normal oxides : These oxides which contain oxygen atom as permitted by the normal oxidation number, i.e., `-2` normal oxide may be acidic, basic, amphoteric or neutral. (b) Polyoxides : The oxides which contain oxygen atoms different than those permitted by the normal oxidation number of `-2`. (i) Peroxides : Two oxygen atoms are linked to each other and oxyegen has `-1` oxidation number. They contain `(O -O)^(2-)` unit. (ii) Superoxodes : These oxides contain `(O-O)^(-1)` unit, i.e., each O-atom has oxidation number `-1//2`. (c) Suboxides : These contain low content of oxygen than expected. (d) Mixed oxides : These oxides are made of two simpler oxides. Which pair of species is referred to as suboxides ?A. CO, NOB. `SO_(2), CaO`C. `N_(2)O, CO`D. `N_(2)O, C_(3)O_(2)`