Problem in the_post_thumbnail

I am seeking for help for this project. in the

<blockquote><section id="portfolio">
      <div class="container">
            <div class="row">

    <?php if( $query->have_posts() ) : while( $query->have_posts() ) : $query->the_post(); ?>

                <div class="col-sm-4 portfolio-item">
                    <a href="<?php the_permalink(); ?>" class="portfolio-link" data-toggle="modal">
                        <div class="caption">
                            <div class="caption-content">
                                <i class="fa fa-search-plus fa-3x"></i>
                            </div>
                        </div>
                       <strong> <img src="images/portfolio/cabin.png" class="img-responsive" alt=""></strong>
                    </a>
                </div>

    <?php endwhile; endif; wp_reset_postdata(); ?>
        </div>
    </div>
</section></blockquote>

I have a problem when inserting “<?php the_post_thumbnail(); ?>” into the “<img src>” section. I want the “<?php the_post_thumbnail(); ?>” will be wrap under the “class=”img-responsive”, because so that the img will fit to the columns what the class have provided. Thank you. this is my email: [email protected]