Which line of code should you use?

You are building a web page for a newspaper publisher.
You have the following requirements:
The web page should split the content into columns that are at least 100 pixels wide.
The number of columns displayed must be set by the browser.
You need to implement the correct CSS properties.
Which line of code should you use?

A.
<div id=”outer” style=”width: 100px; column-fill: balance;”>…</div>

B.
<div id=”outer” style=”width: 100px; column-gap: 10px;”>…</div>

C.
<div id=”outer” style=”column-width: 100px; “>. . .</div>

D.
<div id=”outer” style=”width: 100px; columns: 100px 3″>…</div>