D

Step 1: Understanding Capillary Action: When a capillary tube is placed in a liquid, the liquid rises to a certain height due to the balance of cohesive and adhesive forces. In this case, water rises to 10 cm in the tube due to these forces.
Step 2: Immersing the Tube: When the tube is immersed in water but only 8 cm is above the water surface, the pressure at the upper end of the tube (which is now 8 cm above the water surface) is not sufficient to counteract the cohesive forces holding the water column in the tube.
Step 3: Evaluating the Height: Since the height of the water column can only reach a maximum of 10 cm, the lower section of the tube is already submerged in water. This means that the atmospheric pressure at the open end cannot maintain the water column above 8 cm, causing it not to rise.
Step 4: Conclusion: Therefore, under these conditions, the water does not rise at all in the capillary tube. The correct answer is D.