A、More than 20,000 years. B、Less than 20,000 years. C、More than 2,000 years. D、Less than 2,000 years. A句(5)中，女士提到，书的作者说很难精确地计算人类

W: George, long time no see. What have you been up to lately?
M: No good. I can assure you. (1-1) My homework for my biology class is killing me.
W: (1-2) What is it about? Maybe I can offer you a hand.
M: I am thrilled to hear that. Well, it is about a presentation on my favorite pet. It seems quite easy but you know I am not a fan of any pet.
W: Um, I happened to read a book about dogs and I made some notes in my notebook. Give me a minute to find it.
M: (2) But doesn’t it sound a bit cliche? You know, after all, dogs seem to be the best companion for human beings for thousands of years.
W: That is true, but this book seems to have some new findings about our beloved companion.
M: OK. Give me some details of that please. And by the way, what is the book’s name?
W: Dog Sense: How the New Science of Dog Behavior Can Make You a Better Friend to Your Pet.
M: That is a pretty long name but it sounds appealing.
W: Yes. The whole book takes a very different angle to study dogs.
M: How does the book begin? Maybe I could borrow some ideas from it to build the introduction of my presentation.
W: (3) Well, it begins with pointing out that the relationship between people and dogs is unique.
M: Are you sure? I thought we had a pretty common relationship with dogs. I mean it seems that they are a natural part of our lives.
W: I agree with you but the author thinks that among domesticated animals, (4) only dogs are capable of performing such a wide variety of roles for humans; herding sheep, sniffing out drugs or explosives and being our beloved companions.
M: I get you. But when did that friendship begin?
W: (5) The author says it is hard to be precise about when the friendship began, but a reasonable guess is that it has been going strong for more than 20,000 years.
M: Any hard evidence for that guess?
W: Er, in the Chauvet cave in the Ardeche region of France, which contains the earliest known cave paintings, there is a 50-metre trail of footprints made by a boy of about ten alongside those of a large canid that appears to be part-wolf, part-dog. The author attaches a picture of that scene in his book.
This is the end of Part One of the conversation. Questions 1 to 5 are based on what you have just heard.
1. What is this conversation mainly about?
2. How does the man feel about talking about dogs?
3. How does the book mentioned by the woman begin?
4. Which is NOT mentioned by the woman about what dogs can do for humans?
5. How long have humans and dogs been friends?