A:Having told
B:Having been told
C:She had been told
D:Though he had been told
甲 乙
小丽在使用电饭锅做饭时发现插头发热,原来是插头松动了,继续使用一段时间后,插座烧焦成了如图所示的样子,请你帮他分析产生这种现象的原因是什么?