Answer:
D) A private cloud
Step-by-step explanation:
Note we are told that GuardIN needs a cloud computing option that would allow it to purchase and maintain the software and infrastructure itself.
Thus, to be able to manage the cloud infrastructure itself; it implies buying it's own hardware equipments, which means it is best to use a private cloud computing option.
Doing so would give GuardIN the opportunity to design the cloud storage in a way that all users of the organization can access it without any lag.