The correct answer is A. 5 months.
When a partner draws a fixed sum at the beginning of each month, the interest on total drawings will be equal to the interest of a loan of that amount for 5 months at an agreed rate. This is because the interest on a loan is calculated on the principal amount, and the principal amount is the amount that is borrowed. In this case, the principal amount is the total amount of the drawings, which is the same each month. The interest rate is the agreed rate, which is also the same each month. Therefore, the interest on total drawings will be equal to the interest of a loan of that amount for 5 months at an agreed rate.
Option B is incorrect because it is the interest on a loan of that amount for 5.5 months. Option C is incorrect because it is the interest on a loan of that amount for 6 months. Option D is incorrect because it is the interest on a loan of that amount for 6.5 months.