Which configuration is correct for a DHCP Relay Proxy?

A.
set dhcp relay 1.1.1.1
set dhcp relay 2.2.2.2
set dhcp relay

B.
set dhcp relay proxy
set dhcp relay 1.1.1.1
set dhcp relay 2.2.2.2

C.
set dhcp relay 1.1.1.1 proxy
set dhcp relay 2.2.2.2