Using check boxes to insert data into a database with a text box

I want to insert data selected from check boxes into a database as well as text which the user types into a text box. I want both the check box values and the text to go into the same row on my database.

My code for abc.php:

 <div class="container">
  <h2>Please select the answer below:</h2>
  <form>

    <div class="checkbox">
      <label><input type="checkbox" name="response" value="A">A</label>
    </div>
    <div class="checkbox">
      <label><input type="checkbox" name="response" value="B">B</label>
    </div>
    <div class="checkbox">
      <label><input type="checkbox" name="response" value="C">C</label>
    </div>





<form method="post" name="input" action="insert.php" >
Question ID: <input name="questionid" type="text"/><br/>
<input type="submit" name="Submit" value="insert" />
</form>

my code for insert.php

if(isset($_POST["response"]))
{


    $query = "INSERT INTO response (student_id, response, question_id) VALUES (:studentID, :response, :questionid)";
    $statement = $conn->prepare($query);
    $statement->execute(
      array(
        ':response' => $_POST["response"],
        ':studentID' => $_SESSION['studentid'],
        ':questionid' => $_POST["questionid"]

      )
        );

}

When i press the insert button, nothing happens..... can anyone help?