下列单体中聚合热最高的是()

单项选择题在时间线里，数字前面的正负符号表示：

单项选择题The introductory section usually defines your topic and research focus, describes very briefly the background of previous work in the field, and explains the scope and （ ）. A. importance of your topic B. data collection C. data analysis D. discussion of the results