Errors in trial balance column postings Steps:

• Discount allowed ($900 debit balance) posted to credit column: understates debit total by$900, overstates credit total by $900.
• Bank overdraft ($750 credit balance) posted to debit column: overstates debit total by$750, understates credit total by $750.
• Net effect on debit total: -$900 +$750 = -$150 (debit lower by$150).
• Net effect on credit total: +$900 -$750 = +$150 (credit higher by$150); overall, credit exceeds debit by $300.

Why A is correct:

• Trial balance rule requires debit and credit balances in correct columns; mispostings create imbalance where credit total exceeds debit by net error ($900 -$750 = $300).

Why the others are wrong:

• B: $1590 misadds balances ($900 + $750 =$1650, not $1590) and ignores net effect.
• C: $900 ignores overdraft's offsetting$750 impact.

Final answer: A