The correct answer is: C. lower than the surface of liquid.
When a glass tube is dipped into a liquid, the surface of the liquid inside the tube will be lower than the surface of the liquid outside the tube. This is because the molecules of the liquid are attracted to each other (cohesion) and to the molecules of the glass (adhesion). The stronger the cohesion, the lower the surface of the liquid will be in the tube.
If the cohesion between molecules of a fluid is greater than adhesion between fluid and glass, then the free level of fluid in a dipped glass tube will be lower than the surface of liquid. This is because the molecules of the liquid will be more attracted to each other than to the glass. As a result, the surface of the liquid will be pulled down into the tube.
The other options are incorrect because:
- Option A is incorrect because the surface of the liquid will not be higher than the surface of the liquid outside the tube.
- Option B is incorrect because the surface of the liquid will not be the same as the surface of the liquid outside the tube.
- Option D is incorrect because the surface of the liquid will not be unpredictable.