Answer:

1)Backup

testing technical controls, defensive software, and sensitive assets
all are precious for any company.company wants to secure its sensitive assets.
so, there is a need to have a backup of these sensitive assets.

if there is a need to modify a defensive software.
then the defensive approach is to take a backup of defensive software and then start modification on the separate copy .

it ensures that if there is any mistake in the modification phase then this mistake will be confined with in this copy of defensive software , the original software is intact.

2)high-fidelity virtual environments
having Back up machines is a costly affair, because it includes the following
a)cost of machines/servers
b)power consumption
c)maintenance
d)computer operator is required to operate the machine

if company does not want to spend on back up machines.
cloud vendors offers several services.
company can put its data/software on cloud and can ensure the smooth execution of all the operations.