When is the liquid cooling option required for HP Z420 and Z820 workstations?

A.
When the 1125-Watt power supply is included in the system

B.
When multiple monitors are connected to the system

C.
When SATA storage is included in the system

D.
When E5-2687W high-end Xeon CPUs are included in the system

Explanation:
http://h20195.www2.hp.com/V2/GetPDF.aspx/4AA4-2668ENW.pdf (page 2)