题目内容：
Theauthor'spurposeinpresentingthefirstparagraphis
A．toexplainthebackgroundandnewfeaturesoftoday'sastronomy． B．todiscussindetailthemostrecentachievementsinspaceresearch．
C．tointroducesomenewlyestablishedspacestations．
D．toillustratethattheworldtodayisdifferentinmanyaspectsfromthatofagenera-tionsago．
参考答案：
答案解析：