Should multi-select dropdown/box have an "all" option?


We have a situation where we have an optional "multiple select" box, that looks something like this:

<select size="5" multiple="true">
 ...
</select>

This select box allows you to select multiple items which will then be submitted with the form. I'm wondering, does it make sense to have an "All Options" or default option at the top of the list? Is it redundant? The HTML would look something like this:

<select size="5" id="lol" name="lol" style="width: 100px;" multiple="true">
    <option value="all">All Options</option>
    <option value="1">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
    <option value="4">4</option>
    <option value="5">5</option>
</select>

Here is a jsFiddle demonstrating the HTML and how a "clear fields" button may work: http://jsfiddle.net/m3Zu2/

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