How do I prevent SQL injection from Foldable' AND '1'='1' attack in a Drop Down Menu using Prepared Statement?

Question

I recently did a ZAP report on my project, and there was a high alert saying SQL Injection may be possible through Foldable' AND '1'='1' attack on this particular drop-down menu 'bsearch'. I would like to know if it is possible to solve this issue through Prepared Statement and how do I do it? Thank you.

This is my SQL (PHP)

        $filter = "";
        if(isset($_POST['bsearch']))
        {
            $mod_selected = $_POST['bsearch'];
            $filter = " WHERE catename ='$mod_selected'";
        }
    
        $conn = mysqli_connect('localhost','root','','my_db');
    
        $productsql = "SELECT DISTINCT catename FROM catetable";
        $model_list = mysqli_query($conn,$productsql);
        
        mysqli_close($conn);
    

And this the drop-down menu form.

    <section class = "content feature">
        <section id="featurepage">
            <article id="featurenav">
                <h1>
                    Category
                </h1>
                <form name = "bikeoption" id = "bikeoption" method = "post">
                    <p id = "searchlabel">
                        Select Bike Category: &nbsp;
                    </p>
                    <select name="bsearch" id="bsearch">
                        <?php while ($one_model= mysqli_fetch_assoc($model_list)  ) { ?> 
                        
                        <option value="<?php echo $one_model['catename']; ?>">
                            <?php echo $one_model['catename']; ?>
                            
                        </option>
                    <?php } ?>
                    </select>
                      &nbsp;&nbsp;&nbsp;
                       <input type="submit" value = "Search" id = "bsearchBtn" class = "button">
                </form>
                <br>