1) Dogs has become our allies in this modern world: they hunt, guard, save people in sea and high mountains and even find hidden drugs or defend us from the criminals, yet most of us see them as our best companions to rely on.
2) Since the Ancient Rome, Greece and Egypt domestic dogs got experimented on, as a result we've got a lot* of different breeds to satisfy our needs
3) I know such breeds as Labradors, English Cocker and Springer Spaniels and German Shepherd.
4) The author has listed Greyhounds, Collies, Welsh corgies, St. Bernards and Newfoundland's breeds.
5) This question is an easy one, dogs were the first domestic animal we've got. They are cute, fluffy, understanding and smart. What's not to ask for? They don't require specific food nor place to live, that's why they are best.