The neutral point is a specific point on the aerodynamic surface of an aircraft or airfoil where the pitching moment is not influenced by changes in the angle of attack. This is crucial because when the aircraft's center of gravity is located at the neutral point, the aircraft will exhibit neutral stability, it won't tend to pitch up or down unconditionally as the angle of attack is varied.

The correct response, the torque at the chord line remains constant for changing angles of attack, accurately describes the characteristic behavior at the neutral point. In more detail, "torque" here refers to the pitching moment, which is a type of rotational force. When we say this pitching moment remains constant, it implies that as the angle of attack changes, the aerodynamic forces and moments generated by the wing do not create additional nose-up or nose-down tendencies. This constancy is what defines the neutral point: a stable condition where the aircraft neither pitches upwards nor downwards without an external input, indicating a balance in pitching moment around the chord line.