Sudan Services performed poorly in year 2020 due to the ongoing pandemic and made a large amount of net loss. On December 31, 2021, the company used the income summary account to close the revenue and expense accounts. 

Which of the following statements is true? 

a. The balance of the Income summary account can be debit or credit depending on the company's accounting policy. 

b. After the revenue and expense accounts were closed, there was a debit balance in the Income summary account. 

c. After the revenue and expenses accounts were closed, there was a zero balance in the Income summary account. 

d. After the revenue and expense accounts were closed, there was a credit balance in the Income summary account.