A functioning GRE tunnel interface in Junos requires, at minimum, both a tunnel source address and a tunnel destination address configured together under the tunnel statement of the gr- logical unit, since these two values together define the outer, delivery-layer IP header that will encapsulate every passenger packet sent through the tunnel; the source identifies which of the router's own addresses will originate the encapsulated traffic, and the destination identifies the remote tunnel endpoint the encapsulated traffic must be routed toward across the underlying IP network. The first option correctly supplies both required values in a single, complete statement - source 192.168.1.1 (Router A's own address) and destination 192.168.2.1 (Router B's address) - fully defining the tunnel's endpoints and ensuring the encapsulation and route-resolution process can succeed. The fourth option supplies only the destination and omits the source entirely, which is an incomplete configuration; without an explicit source, Junos cannot always reliably determine which local address to use for encapsulation, particularly on multi-address or multi-interface routers, and the tunnel configuration is left non-deterministic or non-functional as shown. The second option enables the IPv6 protocol family on the tunnel's logical unit, which is irrelevant to a scenario explicitly requiring IPv4 passenger traffic support. The third option attempts to assign a family inet address directly using one of the underlying tunnel endpoint addresses, which conflates the tunnel's own transport addressing with logical-unit protocol addressing and does not by itself establish the required source/destination tunnel definition.
Reference topics: Junos Enterprise Routing - Tunneling, Configuring GRE Tunnel Source and Destination.

Redundant trunk groups are designed to provide link redundancy. If the primary link fails, the secondary link will automatically take over to ensure continued connectivity.
In redundant trunk groups, while regular data traffic is sent over the primary link, Layer 2 control traffic (such as STP, LACP, etc.) is allowed on the secondary link to maintain network stability and protocol operations.
https://www.juniper.net/documentation/us/en/software/junos/multicast-l2/topics/topic-map/redundant-trunk-groups.html

A classic and well-documented gotcha in filter-based forwarding deployments is that the static default route configured inside each forwarding instance frequently references a next-hop address that Junos cannot resolve, simply because the interface and other directly connected routes needed to validate that next hop as reachable exist only in the master inet.0 table by default, not automatically inside the newly created forwarding instance's own table. Since a static route's next hop must be resolvable against routes present within its own routing table to become active, the static default routes inside the ISP-A and ISP-B forwarding instances remain inactive precisely because the necessary interface/next-hop routes were never made visible inside those instances. The standard solution taught for this exact FBF scenario is to configure a routing information base (RIB) group that explicitly imports the relevant interface routes between the master inet.0 table and each forwarding instance's table, allowing the static default route's next hop inside each instance to resolve correctly against the leaked routes and become active. Applying a firewall filter without ever attaching it to an interface accomplishes nothing, since an unapplied filter never evaluates any traffic. Increasing the static route's preference value only affects which competing route wins selection and does nothing to resolve an unreachable next hop. Changing the instance type away from forwarding (to virtual-router) would in fact break FBF entirely, since filter-based forwarding specifically depends on the forwarding instance type working together with a routing-instance firewall filter action. Reference topics: Junos Enterprise Routing - Protocol Independent Routing, Filter-Based Forwarding and RIB Group Route Leaking.

In BGP, routing policies are used to control the flow of routing information between BGP peers.
Option C suggests that import policies are applied after the RIB-In table. This is correct because import policies in BGP are applied to routes that are received from a BGP peer, before they are installed in the local BGP Routing Information Base (RIB-In). The RIB-In is a database that stores all the routes that are received from all peers.
Option D suggests that export policies are applied after the RIB-Local table. This is correct because export policies in BGP are applied to routes that are being advertised to a BGP peer, after they have been selected from the local BGP Routing Information Base (RIB-Local). The RIB-Local is a database that stores all the routes that the local router is using.