document.querySelector( ' #row-as ' ) returns the single element with id row-as.

That element has a classList property with add, remove, etc.

Correct usage:

document.querySelector( ' #row-as ' ).classList.add( ' priority-account ' );

Why others are wrong:

A: querySelectorAll returns a NodeList, not a single element, so it does not have a classList property.

C: DOM elements do not have a classes array or push; they have classList.

D: document.getElementById( ' row-as ' ) is fine to get the element, but there is no addClass method in standard DOM; that’s a jQuery-style API, not vanilla JS.