When the pure solvent diffuses out of the solution through the semipermeable membrane then the process is called:
$A)$Reverse osmosis
$B)$Dialysis
$C)$Osmosis
$D)$Sorption.

Hint: Reverse osmosis is a water purification process that uses a partially permeable membrane to separate ions, unwanted molecules and larger particles from drinking water. Reverse osmosis can eliminate numerous kinds of disintegrated and suspended synthetic species just as natural ones from water, and is utilized in both modern cycles and the production of consumable water.

Complete answer:
Reverse Osmosis is a technology that is used to remove a large majority of contaminants from water by pushing the water under pressure through a semipermeable membrane.
Reverse Osmosis works by using a high pressure pump to increase the pressure on the salt side of the RO and force the water across the semipermeable reverse osmosis membrane, leaving almost all of dissolved salts behind in the reject stream.
Reverse osmosis varies from filtration in that the system of liquid stream is as a natural side effect across a membrane. The prevalent evacuation system in layer filtration is stressing, or size rejection, where the pores are \[0.01\] micrometers or bigger, so the interaction can hypothetically accomplish wonderful effectiveness paying little heed to boundaries like the arrangement's pressing factor and fixation. Reverse osmosis rather includes solvent diffusion across a film that is either nonporous or utilizes nanofiltration with pores $0.001$ micrometers in size.
So, the correct answer is $A)$ Reverse osmosis .

Note:
The concentrated water left over is called the waste or brine. A semipermeable membrane has small pores that block contaminants but allow water molecules to flow through also, it will not remove some pesticides, solvents and volatile organic chemicals including Ions and metals such as Chlorine and Radon.