CAPTCHA does show image but doesn't seem to work

Hi,

I installed the Really simple Captcha plugin and added the code to have the captcha option in my contact form. The image does show up and everything looks fine from the outside but it doesn’t matter what you fill in, the email will be send anyway.

I used this code. Hopefully someone can help me with this.

<div class=”yunik-form-simple-captcha”>
<div class=”f-name”>
[text* your-name watermark “Naam *”]
</div>

<div class=”f-email”>
[email* your-email watermark “Email *”]
</div>

<div class=”f-subject”>
[text your-subject watermark "Onderwerp"]
</div>

<div class=”f-message”>
[textarea* your-message watermark “Bericht *”]
</div>

<div class=”f-captcha”>

<div class=”f-captcha-insert”>
<p>Antispam</p> [captchac captcha-118 size:l]

</div>

<div class=”f-captcha-CONFIRM”>
[text captchar captcha-118 4/4 size:m watermark "Bevestig"]
</div>

</div>

<div class=”bt-contact”>
<span>[submit “Verstuur email”]</span>
</div>

</div>

https://wordpress.org/plugins/contact-form-7/