Final answer:
The key on the alphanumeric keyboard that provides civil navigation capabilities is the CTRL key, which can be used in combination with other keys to perform various functions.
Step-by-step explanation:
The key on the alphanumeric keyboard that gives access to civil navigation capabilities like looking up DAFIF points for direct-to flight, holding and reviewing messages is the CTRL key.
By pressing the CTRL key in combination with other specific keys, you can perform various navigation functions. For example, pressing CTRL + D can access direct-to flight navigation, CTRL + H can access holding patterns, and CTRL + M can display and review messages.
These keyboard shortcuts are commonly used in aviation software and databases to facilitate easy navigation and information retrieval for pilots and air traffic controllers.