Ajax-JSON方法405

Question

I don't understand my error, I want add new data in my file JSON with AJAX :

my script :

function Question(title, fA, sA){
    this.title = title;
    this.fA = fA;
    this.sA = sA;
}


$(function() {
    $('#form').submit(function(event){
        event.preventDefault(); 
        var title = $('#title').val();
        var fA=$('#firstAlternative').val();
        var sA=$('#secondAlternative').val();
        var q1 = new Question(title,fA,sA);
    $.ajax({
        url:"http://localhost:5000/gree/questions",
        type:"POST",
        contentType:"application/json",
        data : JSON.stringify(q1),
        dataType:"json",
        jsonpCallback:'jsonCallback',
        jsonp:false,
        success:function(data){
            alert("HAHAHAHAHHAHAH");
            },
        error: function(){console.log('Error');}

        });
        return false;
});

});

My FORM :

My form is basic, with the good id and with method="POST".

<form id="form"  name="formquestions" style="text-align:center;" method="POST">
    <p>
        <h3>Titre de la question </h3><input type="text" id="title" style="height:50px;font-size:14pt;" size="50" required>
    </p>
    <p>
        <h3>Réponse 1 </h3><input style="height:50px;font-size:14pt;" size="50" type="text" id="firstAlternative" required>
    </p>
    <p>
        <h3>Réponse 2 </h3><input style="height:50px;font-size:14pt;" size="50" type="text" id="secondAlternative" required>
    </p>
    <p>
        <input id="buttonquestion" class="btn-success btn" style="height:50px;font-size:14pt;" type="submit" value=" Créer la question " />
    </p>
</form>

I have the error 405 (not allowed). Not success in ajax, just error...