Which feature supports the HP Z620 workstation’s near silent industrial design?

A.
all-in-one form factor with tool-less access
B.
quiet mini-tower form factor with compact footprint
C.
small form factor chassis optimized for improved air flow
D.
liquid cooled system with tool-less power supply
Explanation:
http://www.augi.com/library/sponsor-spotlight-hp-z-workstations-tested-to-run-yourautodesk-application