Dogs come in all shapes and sizes, from fluffy little lap companions to towering working breeds. But how well do you really know man's best friend? This quiz will test whether you can tell the difference between a Pomeranian and a Papillon, or a Mastiff and a Malamute. Some are easy, others will make even seasoned dog owners second-guess themselves. Only true dog lovers and breed experts will be able to ace this challenge. So, grab a leash, put your paws on the keyboard, and see if you can identify all 40 breeds.