Which step can be used to increase the performance of the critical?

Several virtual machines residing in a resource pool are exhibiting pools and critical virtual machines in the pool appear hung. The resource pool has been allocated exactly 500MHz of CPU and does not have the Expandable Reservation option selected. The cluster in which the resource pool resides has a total of 6000MHz, with 1000MHz available.

Which step can be used to increase the performance of the critical?

A.
Increase the CPU limit on the critical virtual machine.

B.
Increase the CPU reservations on the critical virtual mach

C.
Increase the CPU reservations on the resource pool

D.
Increase the CPU limit on the resource pool

Explanation:
Since several critical virtual machines are hung, and if I understand the question didn’t have limit configured (The resource pool has been allocated exactly 500MHz of CPU and does not have the option selected)

The basic premise is that resource pool reservations are not limits. If the resource pool has been allocated EXACTLY 500 MHz this is a limit not a reservation.

Source: http://www.vmware.com/pdf/vsphere4/r40/vsp_40_resource_mgmt.pdf
Checkout page 39 and the bottom of the page is a table with definitions.

Resource Pool Attributes
……
+ Reservation: Guaranteed CPU or memory allocation for this resource pool. A nonzero reservation is
subtracted from the unreserved resources of the parent (host or resource pool). The
resources are considered reserved, regardless of whether virtual machines are associated
with the resource pool. Defaults to 0.
+ Expandable Reservation: Indicates whether expandable reservations are considered during admission control. If you power on a virtual machine in this resource pool, and the reservations of the virtual
machines combined are larger than the reservation of the resource pool, the resource
pool can use resources from its parent or ancestors if this check box is selected (the default).
+ Limit:  Upper limit for the amount of CPU or memory the host makes available to this resource
pool. Default is Unlimited. To specify a limit, deselect the Unlimitedcheck box.