Which one of the following statements does not relate to the closing transfers when an entity uses the perpetual inventory control system?

Which one of the following statements does not relate to the closing transfers when an entity uses the perpetual inventory control system?

(1) Close off the sales returns account to the sales account.

(2) Close off the settlement discount received account to the cost of sales account.

(3) Close off the trading account by transferring the gross profit to the profit or loss account.

(4) Close off the purchases account to the trading account.

I am leaning towards number 4. But I have no clue about Closing transfers using either inventory system. I believe 4 is correct because the purchases account is used in the periodic inventory control system. Any input will be very appreciated.