公元前和公元后的英语简称是什么（公元前和公元后英语简写）

分别就是

公元前简称是BC，公元前（Before Christ）

The brooch dates back to the fourth century BC.

公元后简称是AD，公元后anno domini

Which of the following can be inferred from paragraphs 2 and 3 about the Volcanic eruptions of the late first millennium?