题目类型：
单选题
题目内容
_____,an object has positive charge when it has lost electrons.
正确答案
C
题目解析
本题考查从句。由题干可知,本句句子主谓语齐全.因此选项应是作为句首的状语。A.That mentioned above是定语从句，排除；B.Which has been mentioned above同样是定语从句，排除；C.As has been mentioned above:是as引导的状语从句。D.What mentioned above名词性从句，排除。答案为C。