Which practice is allowed when it comes to naming a Lightning web component's folder and...

To name a Lightning web component’s folder and associated files, the developer should follow these naming rules:

Must begin with a lowercase letter

Must contain only alphanumeric or underscore characters

Must be unique in the namespace

Can’t include whitespace

Can’t end with an underscore

Can’t contain two consecutive underscores

Can’t contain a hyphen (dash)

The only exception to the last rule is when separating the namespace from the component name in markup. For example, if the component is in the example namespace and has the name myComponent, the folder name should be myComponent, but the markup tag should be . The hyphen character (-) is required by the HTML standard for custom element names. The other options are either invalid or not recommended. For example, including whitespace or using consecutive underscores will cause errors, and using a single underscore will look odd and may confuse developers consuming the component. References: B2B Commerce and D2C Commerce Developer Guide, Lightning WebComponents Developer Guide