Assertion: An electric field is preferred in comparison to magnetic field for detecting the electron beam in a television picture tube.
Reason: Electric field requires low voltage.
A. Both assertion and reason are correct and reason is the correct explanation for assertion.
B. Both assertion and reason are correct but reason is not the correct explanation for assertion.
C. Assertion is correct but Reason is incorrect.
D. Both assertion and reason are incorrect.

Hint: For solving this question we have to understand both assertion and reason so that we can identify the correct option. First we have to use concepts which are very basic in the world of electric fields which require more voltage. By using this concept we are going to answer this question.

Complete step by step solution:
when we talk about assertion in this question it says that electric field is preferred in comparison with magnetic field but electric field for detecting the electron but it's wrong as electric field itself is caused by electric charges so magnetic field is used to detect the carrier charges as when magnetic field is applied the charge carriers gets deflected depending upon the direction between velocity of charge and applied magnetic field and this is due to effect of lorentz force acting on the electron hence, the given assertion is incorrect.

Now, Let us talk about the reason, the reason here says that the electric field requires low voltage which is again incorrect because in order to produce required sufficient amount of electric field to work we need very high voltages across the tube or any material where we need electric field so, greater the voltage applied greater will be the produced electric field, hence reason is also incorrect. So, the final answer is that the assertion and reason are both incorrect.

Therefore, the correct answer is option D.

Note: Electric field is produced when voltage(high) is applied to a conductor and the charge carriers start moving. Magnetic field detects charge and does not produce any charge. This is the only concept used here that one must remember.