Possible answer:

A trial balance will not balance if there is a discrepancy between the total debits and the total credits of the ledger accounts. This can happen for various reasons, such as errors of omission, commission, or principle, posting to the wrong side or wrong account, and incomplete or incorrect recording of transactions. However, the question asks for a specific case where the trial balance will not balance, among four options. Let us examine each option in turn and see which one fits the criteria.

A. A correct entry is posted twice: This error will not affect the trial balance, as both sides of the entry will be equal and opposite, and thus cancel each other out. For example, if Rs. 1,000 is debited to cash account and credited to sales account twice, the trial balance will show Rs. 1,000 on the debit side of cash account and Rs. 2,000 on the credit side of sales account, but the net effect will be zero.

B. Rs. 5,000 received from Harish is posted in the credit side of Hari: This error will affect the trial balance, as it will increase the credit side by Rs. 5,000 without a corresponding debit entry, leading to a difference of Rs. 10,000 (5,000 on the wrong side plus 5,000 on the right side) between the two sides. For example, if Harish paid Rs. 5,000 for goods sold, but the entry is posted as a credit to Hari's account, the trial balance will show Rs. 5,000 on the credit side of Hari's account and Rs. 5,000 less on the debit side of cash account, resulting in a total credit side of Rs. 5,000 more than the debit side.

C. Sales on credit basis is credited to sales account and debited in cash account: This error will not affect the trial balance, as it will increase both sides of the ledger accounts by the same amount, and thus preserve the equality between them. For example, if goods worth Rs. 10,000 are sold on credit, but the entry is posted as a credit to sales account and a debit to cash account, the trial balance will show Rs. 10,000 on the credit side of sales account and Rs. 10,000 on the debit side of cash account, resulting in a total credit side equal to the debit side.

D. Goods of Rs. 2,500 returned to Ram is added into the purchases: This error will affect the trial balance, as it will increase the debit side by Rs. 2,500 without a corresponding credit entry, leading to a difference of Rs. 5,000 (2,500 on the wrong side plus 2,500 less on the right side) between the two sides. For example, if goods worth Rs. 2,500 are returned by a customer named Ram, but the entry is posted as a debit to purchases account, the trial balance will show Rs. 2,500 more on the debit side of purchases account and Rs. 2,500 less on the credit side of Ram's account, resulting in a total debit side of Rs. 2,500 more than the credit side.

Therefore, the correct answer is D, i.e., a trial balance will not balance if goods of Rs. 2,500 returned to Ram is added into the purchases

Goods returned must be subtracted from purchases......