[Plugin: SI CAPTCHA Anti-Spam] Where is the comment textarea?

From the faq:

Sometimes the captcha image and captcha input field are displayed AFTER the submit button on the comment form.
Your theme must have a <?php do_action(‘comment_form’, $post->ID); ?> tag inside your comments.php form. Most themes do. The best place to locate the tag is before the comment textarea, you may want to move it if it is below the comment textarea. This tag is exactly where the captcha image and captcha code entry will display on the form, so move the line to before the comment textarea, uncheck the ‘Comment Form Rearrange’ box on the ‘Captcha options’ page, and the problem should be fixed.

Well, I’m totally an idiot in this thing and didn’t know where I should move the tag. I mean I know where this comment.php located but no clue about the comment textarea. Can someone help point out where I had to move the <? Php do_action (‘comment_form’, $ post-> ID);?> so the captcha image and captcha input appear on the right place (be4 the submit button). Thanks.

BTW I use WP 2.9.2 and Arras theme.