Where do the conditions of the market make unified control necessary or desirable to the public interest?

a. oligopoly

b.

natural monopoly

c. trust

d. cartel

In a natural monopoly, the conditions of the market make unified control necessary or desirable to the public interest. The correct option among all the options that are given in the question is the second option or option "b". A natural monopoly can come into play when there are very high fixed cost of distribution.