Which of the following is the correct way to retrieve a featured image from a post?

Which of the following is the correct way to retrieve a featured image from a post?
Answers:

1.      <!–?php echo get_post_thumb($page->ID, ‘thumbnail’); ?–>

2.      <!–?php echo get_featured_image($page->ID, ‘thumbnail’); ?–>

3.      <!–?php echo get_the_post_thumbnail($page->ID, ‘thumbnail’); ?–>

<!–?php echo get_post_thumbnail($page->ID, ‘thumbnail’); ?–>