73.
The answer is: C
Explanation
The correct option is C: In either Ahmedabad or Delhi.
This is because, according to section 20 of the Indian Contract Act, 1872, the place of performance of a contract is the place where the offer and acceptance are made, or where the parties intend or agree to perform it.
In this case, the offer and acceptance were made in Ahmedabad, where B's agent bought the goods from A. Therefore, A can sue B in Ahmedabad. However, A can also sue B in Delhi, where B carries on business, as per section 20 of the Code of Civil Procedure, 1908, which allows a plaintiff to sue a defendant at the place where the defendant resides or carries on business. Therefore, A has the option to sue B in either Ahmedabad or Delhi.