- As the atmospheric pressure decreases, the pressure on the surface at \(C\) will decrease, allowing the weight of the liquid in the tube to pull it further down against the vacuum between \(A B\).
Hence the level of the liquid in the tube will fall Note:
\(A\) : is incorrect as the level of the liquid falls, this distance will increase.
\(B :\) is incorrect as the pressure on the open surface decreases, the level will rise, increasing the distance. \(C:\) is incorrect as this is a fixed distance, the tube is not free to move closer to or further from the outer container.