Redwood trees are the tallest plants on the earth，reaching heights of up to 100 meters．They are also known for their longevity，typically 500 to 1000 years，but sometimes more than 2000 years．A hundred million years ago，in the age of dinosaurs，redwoods were common in the forests of a much more moist and tropical North America．As the climate became drier and colder，they declined to a narrow strip along the Pacific coast of Northern Califomia．
The trunk of redwood trees is very strong and usually forms a single straight column．It is covered with a soft bark．This bark can be pretty thick，well over two feet in the more mature trees．It gives the older trees a certain kind of protection from insects，but the main benefit is that it keeps the center of the tree harmless from moderate forest fires because of its thickness．This fire resistant quality explains why the giant redwood grows to live that long．While most other types of trees are destroyed by forest fires，the giant redwood actually prospers because of them．
Moderate fires will clear the ground of competing plant life，and the rising heat dries and opens the ripe fruit of the redwood，releasing many thousands of seeds onto the ground below．
New trees are often produced from shoots，little baby trees，which form at the base of the trunk．These shoots grow slowly，fed by the root system of the “mother’’ tree．When the main tree dies，the shoots are then free to grow as full trees，forming a “fairy ring” of trees around the original tree．These trees，in turn，may give rise to more shoots，and the cycle continues．
小题1:Why were redwood trees easier to find in the forests of North America millions of years ago?
A．The trees were taller and stronger．
B．The soil was softer for seeds to develop．
C．The climate there was warmer and wetter．
D．The temperature was lower along the Pacific coast．小题2:Which of the following is a function of the tree bark as mentioned in the passage?
A．It allows redwood trees to bear seeds．
B．It prevents redwood trees from attack by insects．
C．It helps redwood trees absorb water in the air．
D．It makes redwood trees more beautiful and appealing．小题3:Why do redwood trees grow to live that long according to the passage?
A．They have heavy and straight tree trunks．
B．They are properly watered and catered to．
C．They are more resistant to fire damage than other trees．
D．They produce many young trees to maintain their life cycle．小题4:How does a “fairy ring’’ form according to the passage?
A．By killing an old tree．
B．By connecting root systems．
C．By inserting holes into old trees．
D．By surrounding a mature tree．
