Answer: Option 4.
The fresh water is hypotonic and the salt solution is Hypertonic.
Explanation:
Hypotonic solution is a solution that have little dissolved solutes i.e low osmotic pressure compare to other solution. When a cell is put in hypotonic solution, it take in water and the cell swell up and it does not burst due to it's cell wall thereby becoming turgid or hard.
Hypertonic solution is the solution where the concentration of solute is higher outside the cell than inside the cell. Example is saline water.when a cell is placed in Hypertonic solution it will shrinks because it losses water.
Frequency is the term that describes the number of waves passing a point during a certain period of time, frequency is also measured in Hz (hertz).
The oxygen produced by the chloroplasts passes out the cell by Cellular Respiration. So the answer would be D :)