Identify the situation

A raw mango is placed in a concentrated salt solution.

• The salt solution outside the mango is hypertonic compared to the fluid inside the mango cells.
• Therefore, water tends to move out of the mango cells through the semipermeable cell membrane.

Understand the process involved

The movement of solvent molecules (here, water) through a semipermeable membrane from a region of lower solute concentration to higher solute concentration is called osmosis.

In this case:

• Inside mango cells: lower salt concentration, more water
• Outside solution: higher salt concentration
• So water moves from inside the cells to the outside solution.

As a result, the cells lose water and the mango shrinks.

Check the options

A: Osmosis
Correct. The shrinking is due to outward movement of water by osmosis.

B: Reverse osmosis
Incorrect. Reverse osmosis requires external pressure to force solvent in the reverse direction.

C: Diffusion
Incorrect. Diffusion is general movement of particles from higher concentration to lower concentration, but this specific solvent movement through a semipermeable membrane is osmosis.

D: Dialysis
Incorrect. Dialysis involves separation of solute particles through a semipermeable membrane, not the shrinking phenomenon here.

Final answer

The process responsible is: $\boxed{\text{Osmosis}}$

So, the correct option is A.