25 POINTS!!!!!!!

(LC)Which sentence below shows correct use of em dashes?

AIn a-thousand-years, most of our greatest monuments such as they are will have crumbled to nothing.

BIn a thousand years, most of our greatest monuments – such as they are – will have crumbled to nothing.

CIn a thousand years, most of our greatest – monuments such as – they are will have crumbled to nothing.

DIn a thousand years, most of our greatest monuments such as they are will have crumbled-to-nothing.