听力原文：M: Have you ever visited a redwood forest? I recently had a chance to go to Muirwoods National Monument north of San Francisco. W: I've never seen a redwood tree. I really can't imagine how big they are. M: The costal redwoods are the tallest living taings. Some are more than three hundred and fifty feet high. But none of the trees at Muirwoods is that high. You have to go further north in California to see the tallest trees. W: You said that Muirwoods is near San Francisco? I guess it must be quite a tourist attraction. M: Yes, it's less than an hour's drive away, so it's easy to go to. W: I've heard that many redwood trees are thousands of years old. Are the ones in Muirwoods that old? M: The oldest documented age for a coastal' redwood is more than two thousand years. The trees at Muirwoods are 400 o 800 years old. W: Why have they survivied so long? M: They have remarkable resistance to forest fires. Their tough, thick cover protects the trees during a fire. The coastal redwoods also like a damp, foggy climate. W: Then since Muirwocds is near foggy San Francisco, it must be ideal for the trees' survival. I can't wait to go there and see them! (23)