Final answer:
In a freely falling elevator, gravity does not affect the water column in a capillary tube, so the water will not rise, and the water column length will be zero (option A).
Step-by-step explanation:
If a 20 cm long capillary tube is dipped in water and the water rises up to 8 cm, when the entire arrangement is placed in a freely falling elevator, the effective acceleration due to gravity becomes zero. This is because, inside a freely falling elevator, everything experiences weightlessness.
Capillary action is influenced by gravity; it occurs because the weight of the liquid column within the tube is held by the surface tension of the water and the adhesion between water molecules and the tube's surface. When gravity is effectively not present, there is no force causing the water to remain at a certain height within the capillary.
Therefore the shape of the water will be influenced solely by surface tension and adhesion, but there will be no rise due to gravity. Consequently, the water will not rise in the capillary tube, and the correct answer is: A) zero.