You will be given a definition of a task first, then some input of the task.
In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

[header] How to use social distancing for retail businesses in pandemic [title] Set up a mobile queuing system. [step] It can be manual or automated with an application. [title] Issue a queue number to a waiting customer. <sep> (A) [title] Take a customer's order to start the queue. [step] The queue number will then be displayed to the right when a customer gets on line or enters the middle of the line. (B) [step] You will then receive a notification when the queueing process is complete. [title] Decide how to choose a queue option. (C) [title] Send the final customer a significant text message and ask them to register for an application. [title] Assign who will register and name the queue number. (D) [title] Ask the customer to wait nearby safely and ask the customer not to return until alerted. [title] Alert the customer in advance to give them time to return for service.
Output:
D