What does Microsoft consider the most important performance counter to be used to detect
memory bottlenecks?

A.
Disk pages/second

B.
Disk pagedefaults/second

C.
Disk pagefaults/minute

D.
Disk pages/minute

Explanation:
Reference: http://technet.microsoft.com/en-us/library/cc749872.aspx
Memory Bottlenecks and Paging
If you suspect a memory shortage, chart the following Performance Monitor counters:
Memory: Page Faults/sec
Memory: Pages Input/sec

Memory: Page Reads/sec