Which of the following is a characteristic of polyatomic ions?
A) They consist of a single type of atom with a positive or negative charge.
B) They are always neutral in charge.
C) They are composed of two or more atoms covalently bonded, acting as a single ion with a net charge.
D) They cannot participate in ionic bonding.

Though the last part of A is true (polyatomic ions do have a positive or negative charge), the first statement would make it false, as the prefix poly- means 'many', such as in 'polymer'.

B is also false, as ions by definition have a positive or negative charge.

C is correct, as if an ion is polyatomic, it must be consisting of multiple atoms, and if it's an ion, it must have a positive or negative charge.

D is incorrect, as ions are used in ionic bonding, which by definition is the bonding of ions. Polyatomic ions are no different, as they can create compounds like NaClO (sodium hypochlorite, better known as bleach), KOH (potassium hydroxide), MgSO4 (magnesium sulfate, better known as Epsom salt) , among others.