A、They have an unusual sense of responsibility. B、They can respond to humans’ questions. C、They can fall in love just like human

There’s an endless amount of scientific data proving that dogs can develop strong bonds with their owners. People aren’t kidding when they say they "love" their dog, or their dog "loves" them. But we’re rather ignorant about the nature of the relationships that form between dogs.
In an effort to understand the matter further, I spoke with Dr. Marc Bekoff, a researcher and former professor of animal behavior. The doctor’s response to the question of whether or not dogs can fall in love like humans do was a straight "Of course." He went on to say that if love is defined as a long-term commitment meaning dogs seek one another out when they’re apart, they’re happy when they’re reunited, they protect one another, they feed one another, they raise their children together   then of course dogs love each other.
Now our furry friends don’t really experience "romantic" love like in the movies, but they can form deep and lasting bonds with their fellow dogs as well as humans. In fact, evidence shows that most dogs stay with one partner their whole lives. In actuality, love between dogs can be even more intimate than human relationships. When they interact, they aren’t afraid to smell each other and will express themselves clearly and honestly. Once again, it seems we have a lot to learn from dogs.
19. What does the passage say we don’t know much about?
20. What does Dr. Marc Bekoff say about dogs?
21. What does the speaker say about most dogs?