题目内容：

Palaces are known for their beauty and splendor, but they offer little protection against attacks. It is easy to defend a large building, but usually these buildings are not designed with the comfort of a king in mind. When it comes to structures that are both beautiful and defensive, the European castle is a big success.

Castles were originally built in England by the Normans in 1066. They built towers and walls to secure the land they had taken. These castles provided the Normans with a quiet and safe place. They also served as bases of operation for attacks. In this way castles served both defensive and offensive roles. Besides, castles served as offices for governors. Those that were socially beneath the governor would come to report affairs and express their respect. They would address problems, handle business, feast, and enjoy festivities in castles. So castles served as social centers as well.

The first castles were made from earth and wood, and they were likely to suffer from attacks by fire. Then wooden castles were gradually replaced by stone, which greatly increased the strength of these towers and walls. However, attackers could throw flaming objects into castles through the windows or burn the wooden doors. This led to moving the windows and entrances off of the ground floor and up to the first floor to make them more difficult to access.

During the Middle Ages, attacks increased in regularity, so castle defenses were updated. Arrow-slits were added. They were small holes in the castle, which allowed defenders to fire without being hurt. Towers were built from which defenders could provide fire on both sides. The towers were connected to the castle by wooden bridges, so that if one tower fell, the rest of the castle was still easy to defend. A lot of rings of castle walls were constructed, so that even if attackers went past one wall, they would be caught on a killing ground between inner and outer walls. All of these increased the defense of castles.

The end of castles can be attributed to gunpowder. During the 15th century, artillery, a kind of large guns, became powerful enough to break through stone walls. This greatly made the role of castles less effective. Though castles no longer serve their original purposes, remaining castles receive millions of visitors each year who wish to experience the situations of ancient times.

1.What was the original function of castles according to the passage?

A. They served as tourist attractions.

B. They were important social centers.

C. They marked religious ceremonies.

D. They were built for use in emergencies.

2.The reason why wooden castles were replaced by stone castles was that         .

A. stone castles cost less money

B. stone castles offered better defense

C. wooden castles were uncomfortable

D. wooden castles took a long time to build

3.Which of the following showed an improvement in castle defenses?

A. Castles were totally separated by stones.

B. Arrow-slits were made in large quantities.

C. Rings of walls were built to defend the towers.

D. Windows and entrances were moved to the higher floor.

4.What is the best title of the passage?

A. Fancy Living: Learning about Castles

B. Normans: Bringing Castles to England

C. A History of Castles: The Rise and Fall of Castles

D. Defending Castles: Technologies Used to Defend Castles