For the desired look and functionality, I would use a "Custom HTML" control with some CSS styling for the text box to remove the border and leave the line. Here is some code:

<div id="question1">I would like the individual to be able to hear <input type="text" class="answer" id="answer1" /> fill in an entry to a sentence which may have a number of answers - the answer may not be limited.</div>

Add the following to your "CSS and Javascript">"CSS" section of your form. The CSS for the textbox:

input.answer { outline: 0; border: 0; padding: 0; margin: 0; border-bottom: 1px solid #DED9D9;}
input.answer:focus {border-color:none;box-shadow:none;transition:none;}
.hiddens {visibility: hidden !important;position: absolute !important;}

In order for Forms to save the data though, you will have to create a Single-Line field, "hide" it (adding the "hiddens" class, do not use "display:none;" as forms will not save the data), give the field variable a name, and on the change event for "answer1" textbox, add the following javascript:

$(document).ready(function() {
    $(document).on('change', '#answer1', function() { 
        $('li[attr=nameoffieldvariable] input.singleline').val(this.value);
    });
});

 There may be better ways to do this, this is just one way of many.