The given transaction is service provided on account or on credit that means the amount is account receivable. So we shall debit the Accounts Receivable and credit the Service revenue account for the same amount.
The journal entry for the given transaction shall be as follows:
Accounts Receivable Debit $3,100
Service revenue Credit $3,100
Hence the correct answer is:
Debit accounts receivable $3,100, credit service revenue $3,100