Which of the following is a viable solution?

You have a VMware environment and you have noticed that the storage capacity of your
datastores varies widely. You would like to maximize the storage environment by balancing the

space utilization across each of the datastores. Which of the following is a viable solution?

A.
Storage I/O Control

B.
vSphere APIs for Array Integration (VAAI)

C.
vSphere APIs for Storage Awareness (VASA)

D.
Storage Distributed Resource Scheduler (SDRS)

Explanation:
http://www.vmware.com/files/pdf/vmw-vsphr-5-1-stor-drs-uslet-101-web.pdf(page 5,
first para)