Which network driver is required on a VMware ESXi 5.0 host for a vNIC to enter Cisco VM-FEX universal passthrough mode?

Which network driver is required on a VMware ESXi 5.0 host for a vNIC to enter Cisco VM-FEX universal passthrough mode?
A. VMXNET3
B. Vlance
C. Flexible
D. E1000e
E. VMXNET5