Final answer:
The administrator should use a screen flow on the account page to let reps update the shipping address on open orders associated with the account.
Step-by-step explanation:
The administrator should deliver this requirement by implementing option D: a screen flow on the account page that lets the reps choose the updated account shipping address in all open associated orders. This option provides a streamlined solution for reps to update the shipping address on selected orders when the shipping address is changed on the account. By using a screen flow on the account page, reps can easily choose the updated shipping address for all open orders associated with the account.