Which command sequence correctly enables Adapter FEX on Nexus 5000 Series Switches?

Which command sequence correctly enables Adapter FEX on Nexus 5000 Series Switches?
A . switch(config)# install feature-set virtualization
switch(config)# feature-set virtualization
B . switch(config)# install feature-set adapter-fex
switch(config)# feature-set adapter-fex
C . switch(config)# install feature-set adapter-fex
switch(config)# feature-set virtualization
D . switch(config)# install feature-set virtualization
switch(config)# feature-set adapter-fex

Answer: A

Explanation:

install feature-set virtualization : installs the cisco virtual machine feature set on the switch.

feature-set virtualization : enables the cisco virtual machine feature on the switch.

Reference: http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/adapter-fex/513_n1_1/b_Configuring_Cisco_Nexus_5000_Series_Adapter-FEX_rel_5_1_3_N1/b_Configuring_Cisco_Nexus_5000_Series_Adapter-FEX_rel_5_1_3_N1_chapter_010.pdf