Which configuration statement enables an interface on a Junos switch to carry multiple VLANs?

The configuration statement enabling an interface on a Junos switch to carry multiple VLANs is the one that sets the interface to trunk mode. In a trunk configuration, the interface is designed to handle traffic from multiple VLANs by using VLAN tagging. This allows the switch to pass traffic for several VLANs over a single physical link, making it crucial for efficient network design, especially in environments where multiple segregated networks need to coexist over shared infrastructure.

By setting the interface to operate in "trunk" mode with the ethernet-switching family, the switch is instructed to expect and properly manage VLAN tags on incoming and outgoing frames, facilitating the correct routing and separation of traffic between different Virtual Local Area Networks (VLANs). Hence, selecting the option that pertains to setting the interface to trunk mode is essential for achieving such functionality.

Other statements focus on assigning IP addresses or configuring an access mode for a VLAN, which restricts the interface to a single VLAN rather than enabling it to carry multiple VLANs. This makes them unsuitable for the task of allowing multiple VLANs on the interface.