How to hide multiple choice buttons

Hi,

I need my participants to press keys on the keyboard to answer the questions. I'm using multiple choice questions with keyboard responses (using javascript). Now I just need to hide the multiple choice buttons. Here's a screenshot of where I am:

!

I'd like to hide those two buttons.
The javascript code I used for keyboard response is:

Qualtrics.SurveyEngine.addOnload(function() {
this.hideNextButton();

this.hidePreviousButton();

var that = this;

Event.observe(document, 'keydown', function keydownCallback(e) {

var choiceID = null;

switch (e.keyCode) {

case 80: // 'p' was pressed

choiceID = 1;

break;

case 78: // 'n' was pressed

choiceID = 2;

break;

}

if (choiceID) {

Event.stopObserving(document, 'keydown', keydownCallback);

that.setChoiceValue(choiceID, true);

that.clickNextButton();

}
});