Choose the best topic sentence from the four options below. Writ

Choose the best topic sentence from the four options below. Write the corresponding letter of your choice on the answer sheet.
A、We human beings have done quite well in exploring the solar system.
B、The satellite has sent us a lot of valuable pictures of Mars and Saturn.
C、We have progressed from light planes to the landing of men on the moon.
D、Space crafts have landed on Mars and photographed Saturn at close range.
【正确答案】：A
【题目解析】：主题句要符合以下四点：(1)完整性。用完整的句子表达一个完整的思想，这是对主题句起码的要求。(2)一定的具体性和概括性。 主题句要明确、具体、内涵集中，所指单一，不要太笼统，也不要太具体。(3)清晰性。主题句要清晰明了，用词一定要恰当、贴切，不能含糊辞。(4)要有关键词。它不仅制约段落的写作方面和范围，而且是写作的导火线、突破口。关键词可以是一个词、一个词组或一个从句。所以A. We human beings have done quite well in exploring the solar system.最适合当主题句，意思是“我们人类在探索太阳系方面成果喜人”。