The Island of Knights and Knaves

There is an island in which certain inhabitants called "knights" always tell the

truth and others called "knaves" always lie. It is assumed that every inhabitant

of the island is either a knight or a knave.

In the problem there are 3 inhabitants, who are denoted by A, B, C, …. Each of

them makes a statement about the number of knights in a set. Natives denote

sets as {PQR…} (without commas). They also know the empty set {}. Their

vocabulary is rather limited. Generally they talk about even {0, 2, 4, …} and

odd {1, 3, 5, …} numbers.

Who are the knights and who are the knaves?