Which OBP command boots the system and allows use of a different system file?

A.
boot s

B.
boot a

C.
boot /etc/system.new

D.
boot f /etc/system.new

Explanation:

The strictly correct answer is boot a. The a flag is used for alternate boot whereby questions will be asked including which system file to use. However, the command
boot /etc/system.new can also be used as long as the file /etc/system.new is a valid system
file. An alternative would be: boot /dev/null if no system file was available.