What is the name of the process in which an atom loses or gains electrons to form an ion?

Natural killer (NK) cells are large granular lymphocytes that are capable of destroying cells infected by viruses or bacteria and susceptible tumor cells without prior sensitization and restriction by MHC antigens.

Helper T cells (choice A) are a type of white blood cell that helps other immune cells respond to infections but do not directly kill infected or tumor cells.

B cells (choice B) are a type of white blood cell that produces antibodies to fight infections but do not directly kill infected or tumor cells.

Cytotoxic T cells (choice D) are a type of white blood cell that can kill infected or tumor cells but require prior sensitization to do so.

Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.

The concentration of solute particles in the solution is the primary factor that determines the movement of water across cell membranes in osmosis.

Hydrostatic pressure (choice A) can affect the movement of water across cell membranes but is not the primary factor responsible for osmosis.

Temperature (choice C) can affect the rate of osmosis but is not the primary factor responsible for osmosis.

Kinetic energy of liquid water molecules (choice D) can affect the rate of osmosis but is not the primary factor responsible for osmosis.