Virtual private networks (VPNs) are used to provide administrative personnel with secure communication channels through security systems and into trust zones. They allow staff who perform system administration tasks to have access to ports and systems that are not allowed from the public Internet.
IPSec is an encryption protocol for point-to-point communications at the network level, and may be used within a trust zone but not to give access into a trust zone. TLS enables encryption of communications between systems and services and would likely be used to secure the VPN communications, but it does not represent the overall concept being asked for in the question.
SSH allows for secure shell access to systems, but not for general access into trust zones.

Cloud services make exclusive use of virtualization, and systems change over time, including the addition, subtraction, and reimaging of virtual machines. It is extremely unlikely that the exact same virtual machines and images used in a previous audit would still be in use or even available for a later audit, making the tracking of changes over time extremely difficult, or even impossible. Elasticity refers to the ability to add and remove resources from a system or service to meet current demand, and although it plays a factor in making the tracking of virtual machines very difficult over time, it is not the best answer in this case.
Resource pooling pertains to a cloud environment sharing a large amount of resources between different customers and services. Portability refers to the ability to move systems or services easily between different cloud providers.

The other options are the names of the phases, but out of proper order.

The recovery time objective (RTO) is a measure of the amount of time it would take to recover operations in the event of a disaster to the point where management's objectives are met for BCDR.