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《世界知识画报》2004年第一期的文章《一棵树和一座古城——马六甲掠影》中有一幅插图：马六甲河口兀立着一艘西欧人首次远航至马六甲附近时的巨大木船，尽管经历沧桑依然保存完好。结合所学知识推测出这艘船最有可能属于谁的？  [     ]

A．迪亚士          

B．哥伦布         

C．达?伽马        

D．麦哲伦

答案

答案：D

单项选择题

血红细胞、白细胞和血小板均减少，细胞形态大致正常。应首先考虑的是（）

A.再生障碍性贫血

B.缺铁性贫血

C.溶血性贫血

D.失血性贫血

E.巨幼红细胞性贫血
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单项选择题

The sun today is a yellow dwarf star. It is fueled by thermonuclear reactions near its center that convert hydrogen to helium. The sun has existed in its present state for about 4 billion, 600 million years and is thousands of times larger than the Earth.
By studying other stars, astronomers can predict what the rest of the sun’s life will be like. About 5 billion years from now, the core of the sun will shrink and become hotter. The surface temperature will fail. The higher temperature of the center will increase the rate of thermonuclear reactions. The outer regions of the sun will expand approximately 35 million miles, about the distance to mercury, which is the closest planet to the sun. The sun will then be a red giant star. Temperatures on the earth will become too hot for life to exist.
Once the sun has used up its thermonuclear energy as a red giant, it will begin to shrink. After it shrinks to the size of the earth, it will become a white dwarf star. The sun may throw off huge amounts of gases in violent eruptions called nova explosions as it changes from a red giant to a white dwarf.
After billions of years as a white dwarf, the Sun will have used up all its fuel and will have lost its heat. Such a star is called a black dwarf. After the Sun has become a black dwarf, the earth will be dark and cold. If any atmosphere remains there, it will have frozen onto the earth’s surface.

What will probably be the first stage of change as the sun becomes a red giant

A．Its core will cool off and use less fuel.
B．Its surface will become hotter and shrink.
C．It will use up its thermonuclear energy.
D．Its center will grow smaller and hotter.
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