Which flow element can send an email?

The most appropriate flow element that can send an email in Salesforce is the "Send Email" action. Actions in Salesforce flow specifically include a range of predefined operations that can be executed, one of which is sending emails.

When you use the Send Email action, you can specify the recipients, subject, body, and other email properties directly within your flow. This element is designed to handle the sending of emails efficiently and effectively within the context of automation.

The other options do not serve the primary function of sending emails. While "Subflow" can invoke another flow, and a "Screen" element is used to display information or capture user input, these elements do not have the capability to send emails directly. Therefore, an Action, particularly a Send Email action, is the correct choice as it aligns precisely with the requirement to send an email within a flow.