Question

a salt water fish is placed in fresh water. what will happen to the cells of the fish?

Answer 1

The fish will die.

Answer 2

now that they cells are in a hipotonic solution (more solvent than solute)
they will swell up due to osmotic pressure
and finally die

Answer 3

Yeah.

Answer 4

the fresh water is hypotonic - meaning it has a lower solute concentration - than the fish.
the water will enter the fish, to lower the concentration, and the fish cells will burst from too much water.