Why are some types of monopolies considered acceptable while others are not?

Because they must be fair to both the consumer and the seller. Some monopolies create illegal agreement which is why they are not acceptable.

i think the answer is c, rivers.

explanation:

sometimes, borders fall along natural boundaries like rivers or mountain ranges. for example, the boundary between france and spain follows the crest of the pyrenees mountains. for part of its length, the boundary between the united states and mexico follows a river called the rio grande. the borders of four countries divide africa’s lake chad: niger, chad, cameroon, and nigeria.

d.

the northwest territory became the most densely populated area in the u.s.