Introduction:
A universal motor is a type of electric motor that can operate on either direct current (DC) or alternating current (AC) supply. It is commonly used in applications where a high starting torque and variable speed control are required, such as in power tools, vacuum cleaners, and kitchen appliances. The speed of a universal motor depends on various factors, including the applied voltage and current.

Explanation:
The speed of a universal motor is determined by the interaction between the magnetic field produced by the stator and the armature current flowing through the rotor. The direction and magnitude of this magnetic field are influenced by the type of excitation, whether it is DC or AC.

DC Excitation:
In a DC-excited universal motor, the armature current is always in the same direction as the magnetic field produced by the stator. This results in a more efficient interaction between the two, leading to a higher speed. The magnetic field produced by the stator is constant and does not change direction, allowing the armature to rotate at a faster speed.

AC Excitation:
In an AC-excited universal motor, the armature current alternates its direction periodically, opposite to the magnetic field produced by the stator. This causes a less efficient interaction between the two, resulting in a lower speed compared to DC excitation. The changing direction of the armature current causes an alternating magnetic field, which creates a drag on the armature and reduces its rotational speed.

Comparison:
Based on the above explanations, we can conclude that the speed of a universal motor will be higher in DC excitation compared to AC excitation. This is because the constant and unidirectional magnetic field produced by the stator in DC excitation allows for a more efficient interaction with the armature current, resulting in a higher speed.

Dangerously High Speed:
The option 'D' in the given question suggests that the speed of a universal motor will be dangerously high in DC excitation. While it is true that a universal motor can rotate at high speeds under DC excitation, it is not necessarily dangerous. The speed of the motor can be controlled through the applied voltage and the mechanical load on the motor. Additionally, safety measures such as speed regulators and overcurrent protection can be implemented to prevent any dangerous situations.

In conclusion, the correct answer is option 'A' - the speed of a universal motor will be higher in DC excitation than in AC excitation.