What is the command to add another IP address to an interface that already has (at least) one IP address?

What is the command to add another IP address to an interface that already has (at least)
one IP address?

A.
ifconfig eth0:1 192.168.1.2

B.
ipconfig eth0 192.168.1.2

C.
ifconfig eth0 192.168.1.2

D.
ipconfig eth0:1 192.168.1.2