"Large" Images for post thumbnais

Hi.

Why are using the “large”, “full” image for post thumbnails and not the “post-thumbnail”?

My suggestion is to change:

<?php $deserve_image = wp_get_attachment_image_src(get_post_thumbnail_id(get_the_id()),'large'); ?>

<?php if($deserve_image[0] != "") { ?>

<img src="<?php echo esc_url($deserve_image[0]); ?>" width="<?php echo $deserve_image[1]; ?>" height="<?php echo $deserve_image[2]; ?>"  alt="<?php the_title(); ?>" class="img-responsive" />

<?php } ?>

to:

<?php
if ( has_post_thumbnail() ) {
  the_post_thumbnail( 'post-thumbnail', array( 'class' => 'img-responsive' ) );
}
?>