Comprehensive and Detailed Explanation From Exact Extract:
Show best is the status rollup mode designed for groups of redundant or backup devices. It displays the "best" (most available/least severe) status within the group, which is most useful when any one device in the group being up means the group is healthy.
Reference:
Platform Administrator Guide, "Status Rollup Modes: Show Best for Redundant/Backup Device Groups"

Device Studio pollers can use manually defined OIDs when the required OID is not present in the SolarWinds MIB database. SolarWinds documentation specifically describes the option to select Manually Define Object Identifier (OID) , type the OID name and value, select the SNMP get type, and poll the current value from the test node. That makes option A correct. Option B is wrong because if the target device itself does not support or return the OID, SolarWinds cannot poll that value. Option C is wrong because Device Studio can poll multiple OIDs for a given technology. Option D is too broad; SolarWinds says Device Studio values are displayed in existing resources, not that every result becomes a separate widget.

When you create a flow alert in SolarWinds, the object of the alert (such as a specific interface, node, or application) is chosen from the "Create a Flow Alert" panel. Flow alerts are not based on custom SQL queries, require the NetFlow service to be running, and always have associated trigger actions.
Reference:
NTA Administrator Guide, "Creating Flow Alerts,"
" In the Create a Flow Alert panel, you select the object to be monitored for flow-based alerting. "