captcha not coming

Hi all, my WordPress version is 3.8.4 it was not in list so selected 3.8.3.

I am unable to put captcha on my site. I rode FAQ’s and tried but it didn’t worked. I am having <?php do_action('comment_form', $post->ID); ?> in /wp-content/themes/[my_theme]/comments.php. I tried putting it above comment textarea but it not worked.

Thanks in advance

https://ww.wp.xz.cn/plugins/google-captcha/