Maximize osmotic gradient for greater water influx Steps:

• Identify setup: semipermeable bag with solute solution connected to tube, immersed in beaker solution; water moves in via osmosis, raising tube level.
• Determine rise height: depends on osmotic pressure difference (π = iCRT); higher gradient draws more water into bag in 3 hours.
• Evaluate changes: seek option increasing concentration difference between bag (hypertonic) and beaker (hypotonic).
• Select D: replaces beaker solution with water (0 mol/dm³), maximizing gradient for highest rise.

Why D is correct:

• Osmosis drives net water movement from low to high solute concentration; pure water in beaker creates maximum potential difference, increasing water influx per Fick's law of diffusion.

Why the others are wrong:

• A: Larger beaker maintains same concentration gradient but increases external volume, minimally affecting influx rate or height.
• B: Smaller bag reduces internal volume and surface area, potentially slowing osmosis without increasing gradient.
• C: 0.4 mol/dm³ in bag may decrease or maintain gradient depending on original concentrations, not guaranteeing higher rise.

Final answer: D