The correct answer is: A. 3% discount if payment in 15 days, otherwise full payment in 40 days.
A cash discount term of 3/15, net 40 means that the buyer can take a 3% discount if they pay the invoice within 15 days of the invoice date. If they do not pay within 15 days, they must pay the full amount of the invoice within 40 days.
Option B is incorrect because it states that the buyer can take a 15% discount if they pay within 3 days. This is not the correct discount amount.
Option C is incorrect because it states that the buyer will be charged 3% interest if they pay within 40 days. This is not the correct interest rate.
Option D is incorrect because it states that none of the above is correct. This is not the case, as option A is the correct answer.