Which of the following is not a normal balance?

a. a $6,000 credit balance in Discount on Bonds Payable

b. a $9,000 credit balance in Unearned Service revenue

c. a 1,2000 debit balance in Sales Returns and Allowances

d. a 10,000 debit balance in treasury stock

this is the exact question on my homework, I am at a loss on this question