I think the correct answer from the choices listed above is option B. It is the electrons that flow because of electrical attraction and repulsion causes an electric current in a wire. Electrons, which continuously move in wire, are called Electric Current. Hope this answers the question.
To solve this problem we will apply the concepts related to the double slit-experiment. For which we will relate the distance between the Slits and the Diffraction Angle with the order of the bright fringe and the wavelength, this is mathematically given as,

Here,
d = Distance between Slits
m = Order of the fringes
= Wavelength
= 

Rearranging to find the angle,




Therefore the angle that the fourth order bright fringe occur for this specific wavelenth of light occur is 32.19°
Answer:
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