Which of the following expressions can be used to A) define the background and argument of the present studyB) describe research method and procedure C) present results, findingsD) give a conclusion以下几个句子的作用请按照顺序依此填入，答案格式示例：A-B-C-D It is also found that … Although (the research subject) …, (the related problem) … is as yet undetermined. These findings of the research have led the author to the conclusion that …The experiment/investigation in the paper is conducted by adopting …