Paper 1, May June 2009 | Cambridge AS - A Level Biology (9700) Past Papers

The diagram shows a model which can be used to demonstrate mass flow.
X and Y are filled with sucrose solutions of different concentration, causing water to move in or out of X and Y by osmosis or as a result of hydrostatic pressure. Sucrose solution then moves through the tube T joining X and Y.
Which description of this is correct?