If Amoeba is placed in a salt solution. the contractile vacuoles would

Analyze the question: Amoeba is a freshwater organism. It lives in a hypotonic environment (dilute surroundings), so water constantly enters its body by osmosis. The contractile vacuole collects this excess water and expels it (osmoregulation).

Concept: Water moves by osmosis from a region of higher water potential to a region of lower water potential. The rate of water entry depends on the concentration gradient between the cell and its surroundings.

Solution:

1. In fresh water, the surroundings have a much higher water potential than the Amoeba's cytoplasm, so water floods in. The contractile vacuole works hard, filling and discharging regularly.
2. In a salt solution, the surroundings have a lower water potential (the solution is more concentrated). The difference between the cell and its surroundings becomes smaller, or even reverses.
3. Less water enters the Amoeba, so there is less excess water to remove.
4. As a result, the contractile vacuole fills more slowly, so it is formed and discharged less frequently (it may even stop working if the solution is isotonic).

Checking the options:

• A. Bursting more frequently: wrong, since this would happen in very dilute water.
• B. More numerous: wrong, because less water means less need for vacuoles.
• C. Formed less frequently: correct, because less water enters by osmosis.
• D. Grow bigger before they burst: wrong, since there is less water to fill them.

Answer: C

Tip: Remember "salt slows the vacuole." The contractile vacuole's activity follows how much water enters the cell: more dilute surroundings mean a faster rate, and more concentrated surroundings mean a slower rate.