I was going to say double checking mechanism but using both of them (assuming comparing the totals) doesnt actually help in the management of stock. It just helps to identify whether have been errors in the recording of transactions in either the stock control ledger or stock card.
That's what is meant by a double-checking mechanism; something that will reveal errors in recording.
The question is basically asking "Why use both ledger accounts AND stock cards when you could just use a ledger account?". Hence, you need to explain why using a stock card is beneficial (sheepz gave the main reasons).
elaine: Losing only 1 mark on each exam would definitely get you a 50. However, I did worse on the second exam (as did a lot of other people, hence the 78~/90 cutoff for an A+) and only got 44. The question I lost a mark on was the one about why you should classify elements in the balance sheet. I said relevance, as the text book we used last year specifically gave relevance as the reason (could I sue for misleading conduct?

).
I think you guys are going to do a lot better than we did last year.