Answer:
Option (d) is correct.
Explanation:
Setting the high price for the products is not considered as the barrier to the other firms in the market.
In a market condition of monopoly, there is only a single firm in the whole market. Economics of scale, Government authorization, patents and trademark are considered as the barriers to the entry of the other firms.
And if other firms enters with a lower price of the products then they can obtained the significantly large share of the market.