We have shown that C and T are related to the Clifford complex conjugation and Clifford transposition operators, and that they can be exact symmetries only in phenomena in which tensor quantities appear or in those where only spinors or only conjugated spinors are involved. P, CT and CTP can be exact symmetries of spinors. The symmetry operator iQ also exists for electrically charged spinors. This is operator of reflection of the two basis Clifford vectors corresponding to the internal degrees of freedom of spinors.