How dose a DHCP server dynamically assign IP address to host？（）

Addresses are allocated after a negotiation between the server and the host to determine the length ofthe agreement.
B. Addresses are assigned for a fixed period of time.At the end of period，a newquest for an address mustbe made ，and another address is then assigned.
C. Addresses are leased to host.A host will usually keep the same address by periodicallycontacting theDHCP sever to renew the lease.
D. Addresses are permanently assigned so that the host uses the same address at all times.