Thousands of trees over the mountains（) by the farmers last year.

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!

听力原文：M: Have you ever visited a redwood forest？ I recently had a chance to go to Muirw

There are ____________ trees on the hill.

The use of recycled paper is saving thousands of trees from being cut down.

Many () trees must be planted every year.

Wow! There are ＿＿ apple trees（）

（）循环用纸使得成千上万的树木免于被砍伐。

A. Using recycled paper makes thousands of trees be cut down.

B. The use of recycled paper is saving thousands of trees from being cut down.

C. The use of recycled paper can protect thousands of trees.

D. Using recycling paper protects thousands of trees from being cut down

The use of recycled paper is saving thousands of trees from being cut down.

Naturalists and casual observers alike have been struck by the special relationship

between squirrels and acorns (the seeds of oak trees). Ecologists, though, cannot observe

These energetic mammals scurrying up and down oak trees and eating and burying acorns

without wondering about their complex relationship with trees. Are squirrels dispersers

(5) and planters of oak forests or pesky seed predators? The answer is not simple. Squirrels

may devour many acorns, but by storing and failing to recover up to 74 percent of them

(as they do when seeds are abundant), these arboreal o\rodents can also aid regeneration

and dispersal of the oaks.

  Their destructive powers are well documented. According to one report, squirrels

(10)　 destroyed tens of thousands of fallen acorns from an oak stand on the University of

Indiana campus. A professor there estimated that each of the large while oaks had.

Produced between two and eight thousand acorns, but within weeks of seed maturity,

Hardly an intact acorn could be found among the fallen leaves.

  Deer, turkey, wild pigs, and bears also feed heavily on acorns, but do not store them,

(15)　 And are therefore of no benefit to the trees. Flying squirrels, chipmunks, and mice are

Also unlikely to promote tree dispersal---whose behavior. of caching (hiding) acorns below

The leaf litter often promotes successful germination of acorns---and perhaps blue jays,

Important long-distance dispersers, seem to help oaks spread and reproduce.

  Among squirrels, though, there is a particularly puzzling behavior. pattern. Squirrels

(20)　 pry off the caps of acorns, bite through the shells to get at the nutritious inner kernels,

and then discard them half-eaten. The ground under towing oaks is often littered with

thousands of half-eaten acorns, each one only bitten from the top. Why would any animal

waste so much time and energy and risk exposure to such predators as red-tail hawks only

to leave a large part of each acorn uneaten? While research is not conclusive at this point,

(25)　 one thing that is certain is that squirrels do hide some of the uneaten portions, and these

acorn halves, many of which contain the seeds, may later germinate.

 What does the passage mainly discuss?