HTML choose br, br/, br / or /br in line break?

HTML choose <br>, <br/>, <br /> or </br> in line break?
In HTML (up to HTML 4): use <br>
In HTML 5: <br> is preferred, but <br/> and <br /> is also acceptable
In XHTML: <br /> is preferred. Can also use <br/> or <br></br>
Notes:

• <br></br> is not valid in HTML 5, it will be thought of as two line breaks.
• XHTML is case sensitive, HTML is not case sensitive.
• For backward compatibility, some old browsers would parse XHTML as HTML and fail on <br/> but not <br />