Although fog consists of fine drops of water, we cannot see clearly through it because:

To answer this question, the user needs to know about the properties of fog and its effect on light.

Option A is incorrect because total internal reflection occurs when light travels from a more dense to a less dense medium at an angle greater than the critical angle. Fog consists of water droplets that are less dense than air, so total internal reflection does not occur.

Option B is incorrect because the fine drops of water in fog do not polarize the light. Polarization occurs when light waves are restricted to a single plane of vibration, which does not occur in the presence of fog.

Option C is incorrect because opaque objects completely block light, whereas fog allows some light to pass through.

Option D is correct because the fine drops of water in fog scatter most of the light that passes through them. This scattering makes it difficult for light to travel in a straight path, resulting in reduced visibility.

Therefore, the correct answer is:

The Answer is: D