问题：

[单选] How does a DHCP server dynamically assign IP addresses to hosts?（）

A . Addresses are permanently assigned so that the host uses the same address at all times.
B . Addresses are assigned for a fixed period of time. At the end of the period, a new request for an address must be made, and another address is then assigned.
C . Addresses are leased to hosts. A host will usually keep the same address by periodically contacting the DHCP server to renew the lease.
D . Addresses are allocated after a negotiation between the server and the host to determine the length of the agreement.