Which command enables a router to become a DHCP client?

The command ip address dhcp makes a Cisco router interface act as a DHCP client. Instead of manually assigning an IPv4 address and mask to the interface, the router sends DHCP client messages and accepts an address, default gateway information, and other options from a DHCP server when available. The ip helper-address command is different: it configures DHCP relay on an interface so client broadcasts can be forwarded to a DHCP server on another subnet. The ip dhcp pool command builds a DHCP server pool on the router, and ip dhcp client is not the interface command used for this purpose. This is a typical CCNA 200-301 v1.1 IP Services distinction: client, server, and relay roles are separate. When a router must obtain its own interface address dynamically, configure ip address dhcp under the interface and ensure the interface is no shutdown. Therefore the verified answer is A. Reference: Cisco IOS DHCP client configuration guidance.