Answer:

Introduction:
When a metallic surface is irradiated with white light, several phenomena can occur, such as the photoelectric effect and the emission of electrons. In this particular case, the question refers to the observation of a photo-current and the behavior of the maximum kinetic energy of the emitted electrons over time.

Explanation:
The correct answer is option 'A': No photo-current observed. This means that when a metallic surface is irradiated with white light, no flow of electric current is observed.

1. Photoelectric Effect:
When light is incident on a metallic surface, it can transfer energy to electrons in the metal, causing them to be emitted. This phenomenon is known as the photoelectric effect. However, for the photoelectric effect to occur, certain conditions must be met:
- The frequency of the incident light must be above the threshold frequency of the metal.
- The intensity of the incident light must be above a certain minimum value.

2. Photo-Current:
The photoelectric effect can result in the emission of electrons, which can create a flow of electric current if they are collected at an electrode. This current is known as the photo-current. However, in the given scenario, no photo-current is observed. This suggests that either the frequency of the incident light is below the threshold frequency of the metal, or the intensity of the incident light is below the minimum value required to produce a photo-current.

3. Behavior of Maximum Kinetic Energy:
The maximum kinetic energy of the emitted electrons depends on the frequency of the incident light. According to the photoelectric equation, the maximum kinetic energy (K.E.) of the emitted electrons is given by K.E. = hf - Φ, where h is the Planck's constant, f is the frequency of the incident light, and Φ is the work function of the metal.

In the given scenario, there is no information provided about the behavior of the maximum kinetic energy over time. Therefore, it is not possible to determine whether it increases or decreases with an increase in time.

Conclusion:
In summary, when a metallic surface is irradiated with white light and no photo-current is observed, it suggests that either the frequency of the incident light is below the threshold frequency of the metal or the intensity of the incident light is below the minimum value required to produce a photo-current. The behavior of the maximum kinetic energy of the emitted electrons over time is not specified in the question.