What should be used for entry speed when performing spins in the Cessna 152?

When performing spins in the Cessna 152, slow deceleration is key to ensuring a controlled and safe entry into the spin. This technique allows the pilot to decrease the aircraft's speed gradually, preventing sudden changes in airspeed that could lead to an abrupt stall or loss of control. The entry into the spin requires a specific aerodynamic state characterized by low speed, which aligns with how a spin is typically initiated; over-controlling or entering at higher speeds can exacerbate risks and make recovery more challenging.

Engaging in a slow deceleration helps in maintaining better control of the aircraft's attitude and inputs during the spin entry, allowing for a more manageable and predictable spin scenario. The other choices do not align with the standard practices for spin entries; maintaining a constant speed or using slow acceleration could lead to unintended entry dynamics, while "standard speed" does not specify the gradual reduction necessary for spin training. Thus, slow deceleration is the preferred method to ensure safety and control during spin maneuvers in the Cessna 152.