You need to prompt the user to purchase the full version of the app when the trial period expires

You are developing a Windows Store app. You configure the app to allow a free trial period.
You need to prompt the user to purchase the full version of the app when the trial period
expires.
What should you do?

A.
Call the getAppReceiptAsync( ) method of the
Windows.ApplicationModel.Store.CurrentApp object.

B.
Call the getProductReceiptAsync( ) method of the
Windows.ApplicationModel.Store.CurrentApp object and provide the app’s product ID as an
argument.

C.
Call the requestProductPurchaseAsync( ) method of the
Windows.ApplicationModel.Store.CurrentApp object and provide the app’s product ID as an
argument.

D.
Call the requestAppPurchaseAsync( ) method of the
Windows.ApplicationModel.Store.CurrentApp object.