A. price setter
If there is a price setter, most likely they are able to lower the price to a point that competition would be virtually nothing, because everybody would guy from them (the lowest price and good -> high quality).
C. one seller
Monopoly means "to have exclusive... control... of the supply or trade". This means that little to nobody else is able to survive in the trade, and so there would be no competition.
D. products with no close substitutes
As stated above, with nobody else doing business in the area because of little to no profit, (even losing money), there would only be one or two products out there for people to buy.
hope this helps
