Which method would a customer use to display basic information on the form to a user in a client script?

The method g_form.addInfoMessage() is the correct choice for displaying basic information on a form to a user in a client script. This method is specifically designed to add an informational message to the form, which can be useful for providing context or guidance to users as they interact with the form. When this method is called, it will render a brief message at the top of the form, making it easily visible to users.

Using g_form.addInfoMessage() is effective because it not only displays the message but also ensures that it adheres to the visual standards of the ServiceNow interface, improving the user experience. This method allows developers to convey important information without requiring user interaction, ensuring that essential details are communicated efficiently.

Other options, while they might seem relevant, do not provide the specific functionality intended for basic information display as effectively as g_form.addInfoMessage(). For instance, g_form.updateMessage() does not exist as a standard method in the ServiceNow client scripting API, which excludes it from being a viable choice. Similarly, g_form.showMessage() is not a recognized function in this context, and while g_form.setInfo() could imply setting information, it does not clearly correlate with displaying messages like addInfoMessage does.