Which statement about DNS is true?
A.
The client-server architecture is based on push-pull messages.
B.
Query and response messages have different format.
C.
In the DNS message header, the QR flag set to 1 indicates a query.
D.
In the DNS header, an Opcode value of 2 represents a server status request.
E.
In the DNS header, the Rcode value is set to 0 for format error.