A commodity market has a _________ structure, if there is one seller of the commodity, the commodity has no substitute, and entry into the industry by another firm is prevented.
In the following question, some part of the sentence may have errors. Find out which part of the sentence has an error and select the appropriate option. If a sentence is free from error, select 'No Error'. Our office building comprises (1)/ seven floors and a restaurant at the top in an (2)/ area of about eight hundred sq. metres. (3)/ No Error (4)