How many APICs are recommended by Cisco for a Cisco ACI fabric?

How many APICs are recommended by Cisco for a Cisco ACI fabric?

A.
6

B.
5

C.
4

D.
3

E.
2
F. 1

Explanation:

Reference:
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/hw/aci_hig/b_aci_hard
ware_install_guide/b_aci_hardware_install_guide_chapter_010.html(See step 1)