Find all radio groups which haven't been selected
<p>I have a basic quiz/survey type application I'm working on, and I'd like to give the user a prompt before they submit if they haven't answered all the questions. All the questions are multiple choice using radio buttons:</p>

<pre><code>&lt;div class="question"&gt;
    Q1: What is the second letter of the alphabet?
    &lt;div class="choices"&gt;
        &lt;input type="radio" name="question_1" value="1" /&gt; A
        &lt;input type="radio" name="question_1" value="2" /&gt; B
        &lt;input type="radio" name="question_1" value="3" /&gt; C
    &lt;/div&gt;
&lt;/div&gt;
&lt;div class="question"&gt;
    Q2: Which out of these is a berry?
    &lt;div class="choices"&gt;
        &lt;input type="radio" name="question_2" value="1" /&gt; Apples
        &lt;input type="radio" name="question_2" value="2" /&gt; Bananas
        &lt;input type="radio" name="question_2" value="3" /&gt; Carrots
    &lt;/div&gt;
&lt;/div&gt;
&lt;div class="question"&gt; ...etc
</code></pre>

<p>How do you find which groups haven't got an option ticked? Or at least, if there are any which haven't been answered?</p>

<p>jQuery is ok, and even preferred.</p>
