Electromagnetic waves are transverse in nature is evident by
A. polarization
B. interference
C. reflection
D. diffraction

Hint: Recall the concepts of polarization of waves, interference of waves, reflection of waves and diffraction of waves. From all these concepts, check which of them gives the information about the nature of the wave. Hence, check which of the concepts given in the options provide information about the transverse nature of the waves.

Complete answer:
The phenomenon in which two waves superimpose to form a new resultant wave having more or less amplitude than the initial two waves is known as interference of the waves. The reflection of a wave is the changing the direction of a wave in the same medium with the same angle with the normal as that of the angle of incidence but in the opposite direction.
The phenomenon in which a wave bends from the edge of an object is known as diffraction of a wave.From the above definitions, one can conclude that the interference, reflection and diffraction of the waves give the evidence of wave nature and not the transverse nature. Hence, the options B, C and D are incorrect.
The phenomenon in which the vibrations of a wave are restricted in a direction perpendicular to the motion of a wave is known as the polarization of a wave. The waves for which the direction of vibration of the particles in the medium is perpendicular to the direction of motion of the wave is known as transverse wave. This shows that the polarization of waves is possible only for transverse waves. Therefore, the transverse nature of the electromagnetic wave is evident by the phenomenon of polarization.

Hence, the correct option is A.

Note: The students should remember that only transverse waves exhibit polarization. Hence, the polarization only gives the evidence of transverse nature of the wave and not the longitudinal nature of the wave because the polarization only restricts the vibrations of particles in a direction perpendicular to the motion of wave and in case of longitudinal wave particles vibrate parallel to the direction of motion of the wave.