In the following question, the sentence given with blank to be filled in with an appropriate word. Select the correct alternative out of the four and indicate it by selecting the appropriate option.
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'. I am vexed at him (1)/ for what all he has (2)/ done for him till date. (3)/ No Error (4)
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.