What is the initial action a pilot should take before entering Class C airspace?

Before entering Class C airspace, the initial action a pilot should take is to contact approach control. This step is crucial because Class C airspace requires pilots to establish two-way radio communication with the appropriate air traffic control (ATC) before entering. Class C airspace typically surrounds busy airports with a moderate level of air traffic, and ATC provides services to ensure safe and efficient operations for both arriving and departing aircraft.

When a pilot contacts approach control, they are able to receive important information such as traffic advisories, instructions for entry, and any relevant weather updates. This communication ensures that both the pilot and ATC are aware of each other's intentions, which enhances safety in the airspace.

The other options, while potentially relevant in different contexts, do not represent the immediate priority before entering Class C airspace. Requesting a VFR flight plan and notifying ground control are useful actions but are not specifically required to enter Class C airspace. Setting a transponder code is important for visibility on ATC radar but should not take precedence over establishing communication with approach control.