|A) decreasing the radius of the capillary tube||B) increasing the radius of the capillary tube|
|C) increasing the height of water in the vessel||D) None of these|
The water rise in a capillary tube dipped in water is such that the weight of water in the tube above the surface of water in the vessel is equal to (balances) the upward force due to surface tension. So it is clear that if the the bore (radius) to the tube is decreased, the height of the water column in it must be greater. So, (a) is correct.