Omitting both equal sides leaves the trial balance equal, just as substituting one debit account for another does.
Trial-balance equality tests whether the debit and credit balances add to the same amount. It does not show that every transaction was recorded or that each account is correct.
The unadjusted trial balance is a deliberate pre-adjustment checkpoint where errors and missing period-end information should be investigated.
Debit-credit equality does not establish that the entries reflect the underlying events, dates, accounts, or amounts.
Answer: B
Both errors preserve equal debit and credit totals. The omitted entry requires a separate check for missing transactions. The wrong debit requires the account choice to be compared with what the company acquired or consumed. The unadjusted trial balance is one accounting-cycle checkpoint, not a final correctness conclusion.