The correct answer is: A. allowance, permission.
An allowance is a sum of money that is given to someone regularly, especially to help them with their expenses. Permission is the act of allowing someone to do something. In this case, the Commissioner gave the speaker an additional allowance of Rs. 200 a month by allowing him to do something.
The other options are incorrect because they do not make sense in the context of the sentence. Pay is the money that someone is paid for their work. Salary is a fixed amount of money that someone is paid each year for their work. Admittance is the act of allowing someone to enter a place. Agreement is a formal arrangement between two or more people or groups.