Final answer:
The maximum number of users you can create at one time using Salesforce's "Add Multiple Users" option is 10, not 50, 100, 200, or 500 as suggested in the provided options.
Step-by-step explanation:
The maximum number of users you can create at one time using the Salesforce "Add Multiple Users" option is 10. This question might be confusing as it provides options that are not correct in the context of the Salesforce platform's current capabilities. As of the latest updates, the Salesforce interface allows the creation of up to 10 users at once through this particular feature. It's important to note that the numbers listed in the question, such as 50, 100, 200, and 500, are not applicable for this specific task within Salesforce.