When are two-way radio communications required on a flight from Gnoss Airport to Livermore Airport at an altitude of 3,500 feet AGL?

Two-way radio communications are required upon entering Class D airspace because this type of airspace is designated around airports with an operational control tower, and communication with that tower is essential for maintaining safety and order. Class D airspace typically extends from the surface up to 2,500 feet above the airport elevation, and pilots must establish communication with the control tower before entering this airspace to receive traffic advisories and instructions.

In the scenario of flying from Gnoss Airport to Livermore Airport at an altitude of 3,500 feet AGL, it's likely that the route involves passage through the Class D airspace surrounding Livermore Airport. Therefore, effective communication with air traffic control is required as the pilot approaches and enters this airspace, ensuring proper coordination with other aircraft and the control tower.

Other options focusing on cruising altitudes, the entire flight, or only during takeoff and landing are misleading in this context. While two-way radio communication is important at higher altitudes or during specific phases of flight, it is specifically mandated when entering Class D airspace for the safety and regulation of all air traffic in the vicinity of an airport with a control tower.