The angle of attack of a
propeller has the same definition as the angle of attack of an aerofoil - the
angle between the chord line and the relative airflow. The problem with a
propeller is the relative air flow keeps changing direction.
The two factors that determine the direction of the relative airflow are
rotational velocity of the segment (the RPM) and the forward speed (TAS)
The angular velocity option is incorrect because it is virtually the same as
the rotational velocity of the segment. Angular velocity is measured in degrees
per second so it could be equated to the RPM as well.