A

Step 1: The shorter limb of the tube is covered with an impermeable membrane, meaning gas cannot pass through it.
Step 2: The tube is filled with hydrogen and positioned with the open end downwards, causing the gas to exert pressure on the membrane in the shorter limb due to the weight of the hydrogen column.
Step 3: The pressure in the shorter limb will be lower since there is no external atmospheric pressure acting on the membrane, resulting in the membrane pushing upwards towards the hydrogen gas to maintain equilibrium.
Step 4: Thus, the position the membrane will adopt is upward towards the hydrogen in the shorter limb of the tube.
Therefore, A.