What does it mean to privatize?

a. to keep a government secret

b. to sell a state-run firm to an individual

c. for the government to take a laissez-faire view

d. for individuals to run 4es

To "privatize" means to make something private, something that was not private before, but instead was public - that is, owned by the people (as represented by their government).

So to privatize means to b. to sell a state-run firm to an individual (so to make it a private property)