When creating a new policy to accept and redistribute routes into your Interior Gateway Protocol (IGP), the route-filter match criteria is used to identify the route prefixes to select. The route-filter statement specifies which prefixes should be matched in a policy. This allows for precise control over which routes are accepted and redistributed, facilitating efficient and secure routing policies within the network.
Reference:
"show | display set | match ge-0/0/2" indicating command examples and match criteria from Useful Juniper Commands.txt.
Juniper official documentation: Routing Policy and Firewall Filters Configuration Guide.

Junos OS can store up to 50 rollback configuration files, making B the correct answer. These rollback files allow administrators to revert to previous configurations, providing a safety net that facilitates recovery from configuration errors or undesired changes

In Junos OS, the # prompt indicates that you are in configuration mode. This mode is used for making changes to the configuration of the device.
Reference:
"The # prompt indicates that you are in configuration mode."

To advertise a default static route into OSPF on router R1, a routing policy should be configured. This policy would typically include a statement to match the default route (0.0.0.0/0) and then apply an action to set the route as an OSPF external type, which would then be redistributed into the OSPF domain. The routing policy is a set of conditions and actions that determine how routes are imported into or exported from the routing table and how routes are shared between routing instances or routing protocols. After defining the policy, it must be applied to OSPF under the export section of the OSPF configuration on R1. This process will allow R1 to announce the default route to other OSPF routers in the network, which then can use it as a gateway of last resort to reach the Internet or other networks not explicitly known to the OSPF domain.

https://www.juniper.net/documentation/us/en/software/junos/user-access-evo/user-access/topics/topic-map/junos-os-login-class.html#:~:text=You%20can%20define%20any%20number,to%20an%20individual%20user%20account.
In Junos OS, each user account can be assigned only one login class. Login classes in Junos OS define the permissions for users, controlling what they can access and modify within the system. This setup helps in maintaining a clear and secure access control mechanism.
Reference:
Junos OS Documentation on User Accounts and Login Classes.