Which statement is correct about logical units on Juniper Router interfaces?

A. Logical units are used only when a Layer 2 identifier is present such as a VLAN.

B. A logical unit of 0 is required when using a frame-relay DLCI.

C. A logical unit is always required.

D. Logical units are not required unless ATM or 802.1Q VLAN tagging is configured.

Many router vendors refer to a logical unit as a subinterface; they do not require a subinterface on every physical interface, whereas a Juniper Networks router does.

Note: All router interfaces that will send and receive transit traffic require a logical unit to be configured. This logical unit creates a division of the physical interface into multiple parts.

References: https://www.safaribooksonline.com/library/view/junos-enterprise-routing/9781449309633/ch04s03.html