Which sentence below shows correct use of em dashes? (4 points)

Select one:

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.