You’re wrong. Correct answer is A.
Ref: vsphere-50-configuration-maximums.pdf, page 2
Table 1. Virtual Machine Maximums (Continued)
Virtual Peripheral Ports
USB controllers per virtual machine 18
USB devices connected to a virtual machine 20
Parallel ports per virtual machine 3
USB 3.0 devices per virtual machine 1
Correct answer is C. 1 controller per VM, 20 devices per VM.
You’re wrong. Correct answer is A.
Ref: vsphere-50-configuration-maximums.pdf, page 2
Table 1. Virtual Machine Maximums (Continued)
Virtual Peripheral Ports
USB controllers per virtual machine 18
USB devices connected to a virtual machine 20
Parallel ports per virtual machine 3
USB 3.0 devices per virtual machine 1
Note: USB 3.0
I quote from the same table:
USB 3.0 devices per virtual machine 20
The 10 annotation states:
10. Guest operating systems might have smaller limits than allowed by vSphere
In the end, I think the correct answer is C.