The correct answer is D. All of the above.
The current in a gravity controlled instrument is proportional to the balancing weight, the deflection angle, and the sine of the deflection angle. This is because the current is proportional to the force on the coil, which is proportional to the balancing weight and the deflection angle. The sine of the deflection angle is needed to account for the fact that the force on the coil is not perpendicular to the magnetic field.
The crowding scale is a result of the fact that the current is proportional to the balancing weight, the deflection angle, and the sine of the deflection angle. This means that the current is very sensitive to small changes in the balancing weight, the deflection angle, or the sine of the deflection angle. This can make it difficult to read the scale accurately.
To reduce the crowding of the scale, one can use a larger coil, a stronger magnet, or a lower sensitivity. One can also use a different type of instrument, such as a strain gauge or a potentiometer.