How to capture links made by javascript components?

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C#

HTML

Hi,
These codes make an image by java. How to capture the link of these images in languages like C# using WebBrowser control in which you have access to just HTML document text.

<script>
	var RecaptchaOptions = {
	theme: 'custom',
	lang: 'ir',
	custom_theme_widget: 'recaptcha_widget'
};
</script>
<div id="recaptcha_image"></div>
<span class="recaptcha_only_if_image">نوشته:</span>
<input type="text" id="recaptcha_response_field" name="recaptcha_response_field" />
<script type="text/javascript" src="http://api.recaptcha.net/challenge?k=6LfdmAsAAAAAAPb_3Zn53hlv5fR3oUS0FeXc7a9h&lang=en"></script>

thx