In the process of the client applying for an IP address through DHCP and assigning an IP address to the DHCP server, which of the following messages are usually unicast? (Multiple Choice)

In the process of the client applying for an IP address through DHCP and assigning an IP address to the DHCP server, which of the following messages are usually unicast? (Multiple Choice)
A . DHCP OFFER
B . DHCP REQUEST
C . DHCP DISCOVER
D . DHCP ACK

Answer: AD