2020年海南专升本考试费每人每科40元

右心室出口周缘附着的是 （　　）

A.二尖瓣

B.三尖瓣

C.主动脉瓣

D.肺动脉瓣

E.半月瓣

随机事件A与B互不相容，则P(AB)=()．

A.P(A)+P(B)
B.P(A)P(B)
C.1
D.0

下列选项中，不会导致继承人继承权的丧失的是（）

A.故意杀害被继承人的

B.杀害其他继承人的

C.遗弃被继承人，情节严重的

D.虐待被继承人，情节严重的

To us it seems so natural to put up an umbrella to keep the water off when it rains．But actually the umbrella was not invented as protection against rain．Its first use was as a shade against the sun．
Nobody knows who first invented it,but the umbrella was used in very ancient times．Probably the first to use it were the Chinese,way back in the eleventh century B.C.
We know that the umbrella was used in ancient Egypt and Babylon as a sunshade．And there was a strange thing connected with its use:it became a symbol of honor and authority．In the Far East in ancient times,the umbrella was allowed to be used only by royalty or by those in high office.
In Europe,the Greeks were the first to use the umbrella as a sunshade．And the umbrella was in common use in ancient Greece．But it is believed that the first persons in Europe to use the umbrella as protection against the rain were the ancient Romans.
During the Middle Ages,the use of the umbrella practically disappeared．Then it appeared again in Italy in the late sixteenth century．And again it was considered a symbol of power and authority．By 1680,The umbrella appeared in France,and later on in England.
By the eighteenth century,the umbrella was used against rain throughout most of Europe．Umbrellas have not changed much in style during all this time,though they have become much lighter in weight．It wasn't until the twentieth century that women's umbrellas began to be made,in a whole variety of colors.

Which of the following is the best title for the passage?

A.The Invention of Umbrell
B.The History of Umbrell
C.Umbrella--A Symbol of Hono
D.Who Used Umbrella First?