下面摘录了某些同学实验记录本中有关实验现象描述的一部分，其中正确的是（ ）
A．将带有铜绿的铜丝在酒精灯火焰上灼烧，铜丝表面变黑
B．镁条在氧气中点燃，发出耀眼的强光，同时生成黑色固体
C．点燃一氧化碳气体，看到蓝紫色火焰，同时放出大量的热
D．将硫酸铜溶液滴加入到氢氧化钠溶液中，产生红褐色沉淀
答案：A
本考点中既有金属的性质和碱的性质，又有一氧化碳的性质和实验方案的评价，考查的比较全面，碱式碳酸铜在加热的条件下生成氧化铜和水和二氧化碳，现象是绿色变黑色，故选项A正确；镁条燃烧的现象是：发出耀眼的强光，放出热量，同时生成白色固体，故选项B错误；一氧化碳燃烧的现象是：发出淡蓝色火焰，同时放出大量的热，生成能使澄清石灰水变浑浊的气体，故选项C错误；硫酸铜溶液滴加入到氢氧化钠溶液中，产生蓝色沉淀，故选项D错误。
| 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. |
The word "there" underlined in Paragraph 4 refers to ______ .
A．our own planet
B．the outer surface of the sun
C．the core of a black dwarf
D．the planet mercury